Data-Block Spread Spectrum Communications System

ABSTRACT

A spectrum spread communication method includes a step of generating a data block formed by a plurality of M bits of transmission data in the CDMA communication method, a step of modulating an orthogonal sinusoidal wave by the repeated series of the data block to generate a spread symbol, a step of transmitting the symbol, a step of performing reverse spread of the reception input by using the orthogonal sinusoidal wave, thereby completely isolating the multi-user component including the multi rate.

TECHNICAL FIELD

The present invention relates to code division multiple accesscommunications systems (CDMA) using spread-spectrum modulation which canreduce white noise disturbance admixed in a transmission process andinterference generated in a multi-user signal separation process, canenhance further the frequency-utilization-efficiency, and can reduce apower-bandwidth-product. In this case, the modulation/demodulationtechnology for transceivers of mobile communications systems where thespread-spectrum modulation is applied to transmit-data BPSK signals istaken as an example to explain user-separating techniques for amulti-user receiver.

BACKGROUND ART

Spread-spectrum communications is a system using spreading modulationtechnology where spreading-sequences are modulated by transmit-data toproduce transmit-symbols. Due to this spreading modulation, adata-sequence spectrum having a relatively narrow bandwidth is spread toa wide frequency band and then this spread signal is to be transmitted.In a region (cell or sector) where a base-station (BS) providescommunications services, there are a plurality of user-stations. Such acommunications system is excellent in that a low transmit-power per unitfrequency is consumed, disturbance to other communications can be keptat a relatively low level, and the system has inherently strongresistance to (AWGN) mixed in a transmission process andinter-user-station interference-noise incoming from mobile stationsother than a desired station. However, since communications of a largenumber of stations share the same time-slot and the same frequency band,there is a problem in which an increase in the number of users to beaccommodated per unit band is difficult due to theinter-station-interference-noise. That is to say, disturbance caused bysuch noise decreases frequency-utilization-efficiency and increasesrequired transmit-power.

FIG. 16 is a block diagram illustrating the general composition of amobile communications system which performs direct-sequencespread-spectrum (DS-SS) communications via a radio communicationschannel. Here, a transmitter TK_(k) of the k-th user u_(k) in a cellmodulates binary transmit-data b_(k) to obtain a Binary Phase ShiftKeying (PBSK) symbol s_(KBP), and then by modulating thespreading-sequence c_(k) of the k-th user by s_(KBP) to produce a spreadspectrum signal s_(k) ⁰. A radio-band signal s_(k) is produced bymodulating a carrier wave f_(C) by s_(k) ⁰. Thereafter, s_(k) istransmitted through a radio communications channel. Generally,pseudo-noise (PN) sequences, each is different from one another, areused as spreading sequences, the k-th one is denoted by c_(k), so that areceiver may discriminate addresses of the respective users.

A receiver RX receives, through an antenna, a multiplexed receivedsymbol r which includes, as the components, spread-spectrum-modulatedsequences received from all the users, and demodulates r by a localcarrier-wave f_(C) to obtain a base-band-symbol r_(RR).

Receiver RX applies base-band-symbol r_(BB) to a matched filter MF_(k)matched to a pilot response p_(k) for producing a soft-output {tildeover (b)}_(k). (Switch S illustrated is used so that PRM may receive thepilot signal in time division manner.) Soft-output {tilde over (b)}_(k)is applied to a hard decision circuit DEC so as to be compared with athreshold value, thereby received binary data {circumflex over (b)}_(k)is detected. (This is called “correlative detection”).

Detected data {circumflex over (b)}_(k) is applied to a synchronizingcircuit SYNC which controls a generating timing of the pilot response sothat the component of transmitted symbol s_(k) contained in multiplexedreceived symbol r may be synchronized with the phase of p_(k). In TX andRX in FIG. 16, the arrangement of sequential order of multiplyingfunctions of carrier-wave f_(C) ({circumflex over (f)}_(C)) andspreading sequence c_(k) are often exchanged each other.

The above-described receiver is composed of different multiple matchedfilters arranged in parallel to detect respective user specific symbolcomponents. In this system, due to a cross-correlation value between thek-th sequence c_(k) allocated to a user and the k′-th (different)sequence c_(k) (k≠k′) allocated to another user, a matched filtersoft-output {tilde over (b)}_(k) contains a large interfering noiseincoming from the other users. A pilot-response p_(k) influenced by amulti-path channel gain between a transmitter and a receiver is anelement generating inter-user-interference stated above, and aninter-user cross-correlation between a pair of such pilot responsestakes a larger value than that between the correspondingspreading-sequences themselves. Furthermore, the multi-path waves due toadjacent symbols which a desired user and the other users havetransmitted generate an inter-symbol interference.

AS a result, it is impossible to increase a user population K comparedto the sequence length (processing gain) L. For this reason, it isimpossible to increase the frequency utilization efficiency. In order tosuppress disturbance due to the above-mentioned interfering noise,technology on multi-user receivers for performing user signal separationand inter-symbol interference separation by utilizing a system ofde-correlating sequences have been studied. However, sufficient noisesuppression effect can not be achieved.

Here, let's explain 7 preceding techniques in a close relation to thisinvention.

(P-1) Mamoru Sawahashi, Yoshinori Miki, Hidehiro Andoh, and KenichiHiguchi: “Pilot Symbol-Assisted Coherent Multistage InterferenceCanceller Using Recursive Channel Estimation for DS-CDMA Mobile Radio”IEICE Trans. Commun., Vol. E79-B, No. 9, pp. 1262-1270, (1996-09.)

(P-2) Mitsuhiro Tomita, Noriyoshi Kuroyanagi, Satoru Ozawa, NaokiSuehiro: “Error rate performance improvement for a de-correlating CDMAreceiver by introducing additional dummy pilot response”, PIMRC'02,Lisbon (2002-09)

(P-3) Hiroki Inokura, Mitsuhiro Tomita, Kohei Otake, NoriyoshiKuroyanagi, Satoru Ozawa, and Naoki Suehiro: “A CDMA-MIMO System withMultiple-Dimension-De-correlating-Detectors”, VTC2003-Fall, ORLANDO(2003-10)

(P-4) Mitsuhiro Tomita, Noriyoshi Kuroyanagi, Naoki Seuhiro, ShinyaMatsufuji, “Anti-heavy-interference performance of a lone pilot assistedCDMA system”, SCI'2000, Orland, Fla. U.S.A. (2000-07)

(P-5) Shengli Zhou, Georgios B. Giannakis, and Christophe Le Martet:“Chip-Interleaved Block-Spread Code Division Multiple Access” IEEETransaction on Communications, Vol. 50, No. 2, pp. 235-248 February 2002

(P-6) Geert Leus and Marc Moonen: “MUI-Free Receiver for a SynchronousDS-CDMA System Based on Block Spreading in the Presence ofFrequency-Selective Fading”, IEEE Transaction on Signal Processing, Vol.48, No. 11, November 2000

(P-7) Yutaro Minami, Ken'ichi Asano, Kohei Otake and NoriyoshiKuroyanagi “FIBS/CDMA-Frequency Interleaved Multiplexing Block-SpreadCode Division Multiple Access Systems” IEICE Trans. on Fundamentals Vol.J87-A No. 7 pp. 1005-1016 2004-07

System (P-1) intends to upgrade the function of the k-th matched filterMF_(k) to detect a data of the k-th user u_(k) in the system explainedwith FIG. 16, and uses a receiver equipped with an interferencecanceller shown in FIG. 17. At an interference canceller IC-1 (the firststage), a matched filter bank MFB generates estimated transmit-data(soft-outputs) {tilde over (b)}_([k]) of all the users except that ofthe (k1)-th user by using the first stage received input r¹ and apilot-response supplied from a pilot response memory PRM. By usingsoft-outputs {tilde over (b)}_([k]), the first interference generatorI-GEN₁ generates a replica (pseudo input) φ_([k]).

By subtracting φ_([k]) from input r¹, interference canceller IC-1generates a soft-output {tilde over (b)}_(k1). By making soft-output{tilde over (b)}_(k1) on the hard decision, is obtained a detectedoutput {circumflex over (b)}_(k1) with which a corresponding replicaφ_(k1) is generated with the second interference generator I-GEN₂. To acanceller (called the second stage) IC-2, is applied an input r² whichis made by subtracting replica φ_(k1) from received input r¹. CancellerIC-2 repeats to apply the same operation to input r² as that IC-1 hasdone.

In this method, due to existence of large cross-correlations betweenpilot-responses of respective users, large interference componentsresultantly remain in the soft-outputs. For this reason, an error ratecan neither sufficiently reduce, nor the user population to spreadingfactor ratio (K/L) can sufficiently increase.

The functional block diagram of a related multi-user receivercorresponding to system (P-2) is shown in FIG. 18( a). Each user'stransmitter transmits pilot symbols by inserting them in a data symbolframe, for example in time division manner. A receiver receives thepilot symbol of each user u_(k). And the receiver always prepares thehighly precise pilot responses p_(k) (convolution product of spreadingsequence and channel gain characteristic) between respective of all theusers and the receiver, and stores them in a memory PRM.

In broadband wireless transmission, delayed waves which have arrived viaa large number of multi-paths generally are received. Received signalcomponents appear outside of a transmit-symbol period T_(S) due todelayed waves. They are inter-symbol interference ISI which givesdisturbance to the succeeding symbols of desired user and the otherusers. In order to avoid this disturbance, That is to say, a guard addedsequence is produced by appending a guard sequence to a core-sequence,and then an extended symbol is made by multiplying the guard addedsequence by transmit-data as a transmit-symbol.

A receiver extracts a received core-symbol r illustrated which is anonly components received on the core-sequence period. Foresaidinterference ISI can be avoided for both down-link transmission ofsynchronous reception, and up-link transmission of quos-synchronousreception controlled so that all the user's signals may arrive almostsimultaneously, if the guard sequence of which length is longer than themaximum delay time τ_(DM) is used.

Under these conditions, a received core-symbol r is given by thefollowing equation,

$\begin{matrix}{r = {{\sum\limits_{k = 0}^{K}\; {b_{k}p_{k}}} + x}} & \left( {E\text{-}1} \right)\end{matrix}$

where b_(k) is a transmit-data of u_(k), and x is white noise (AWGN)included in received symbol r. By using a pilot-response-matrix Pconsisting of pilot-responses p_(k) of all the users, Eq. (E-1) issolved by an analyzer AYZ (DD, de-correlating detector) in FIG. 18( a)to obtain a soft-output {tilde over (b)}_(k)=b_(k)+Δb_(k) correspondingto the transmit-data, where Δb_(k) is an error contained in the softoutput corresponding to AWGN. This system has an advantage such that theinfluence of interfering waves can be almost removed.

However, it becomes impossible to generate a guard added symbol, in acase of T_(S)<τ_(DM) for the maximum delay time τ_(DM) due to thereduction of a transmit-symbol period T_(S), when the data transmissionspeed increases using system (P-2). Hence, there is a problem such thatan increase of the transmission rate causes spectral efficiencyreduction and an increase in the transmit-power even for a condition ofT_(S)>τ_(DM).

System (P-3) is of using an MMSE-D (Minimum Mean Square Error Detector)shown in FIG. 18( b). This detector uses a similar method to that ofabove-mentioned method DD, such as to produce a system of de-correlatingequations, to obtain a soft output of the transmitted data by ananalyzing circuit AYZ(MMSE), and to detect the soft-output. SystemMMSE-D is to add an additive term to matrix P to enhance the regularityof matrix P, thereby suppressing AWGN multiplication effect occurred inthe analyzing process. This system brings an improvement effect to theanalysis such as to minimize the sum of errors due to the interferencenoise and the AWGN. However, it is difficult to increase the data-ratesimilarly to system (P-2).

In addition, system (P-3) contains (technology) a multi-user receivingfunction of user signal separating function by an MMSE system andmulti-input and multi-output (MIMO) system using a reception outputobtained from multiple receive antennas. By using multiple transmit- andmultiple receive-antennas, this system can acquire an enhanced space andtime diversity effect.

That is to say, a concatenated received vector with N_(R)L chips isproduced by using received core-symbols, each having L chips, receivedfrom N_(R) piece of the receive-antennas.

On the other hand, a concatenated pilot response is beforehand producedusing pilot responses which have received via the respective antennasfrom each of the users. The concatenated received vector stated above isanalyzed by a pilot response matrix made of the concatenated pilotresponses, to perform user signal separation and data-detection. Thelarger the numbers of receive-antennas are used, the larger the userpopulation can be accommodated.

However, system (P-3) has the previously mentioned problem caused by theguard sequences, similarly to system (P-2).

In system (P-4), a spreading sequence with L chips is assigned to eachuser. Each user transmitter produces a repeated sequence made byrepeating the assigned spreading sequence N times and makes (M+1) piecesof base-band-symbols which are produced by modulating this repeatedsequence by respective of M bit transmit-data and 1 pilot information.Each user produces modulated outputs by modulating (M+1) pieces oforthogonal carrier waves, prepared by the system, by respective of thesebase-band-symbols, producing a (multiplexed) transmit-symbol byconcurrently summing the modulated outputs and transmitting it. (Thismethod appears a kind of data-block transmission).

If each user uses a carrier wave out of different orthogonalfrequencies, respective of M pieces of symbol components can beseparated (separation of intra-user components), because each of abovestated base-band-symbols consisting of the repeated components has acomb-form-spectrum. Each of the separated component obtained in thisway, consists of a component made by multiplexing K pieces of the dataand the pilot symbols which K users have transmitted using an identicalorthogonal carrier wave.

If applying demodulation processing of separating intra-user-componentsto a multiplexed received symbol made by multiplexing K pieces ofsymbols which K (K≦L) users have transmitted using an identicalorthogonal carrier wave, a demodulated multiplexed core-symbol isobtained. When applying the technique of de correlation circuit ofsystem (P-2) to this separated symbol, the inter-user separation can beachieved. Since each user's pilot symbol is transmitted using theidentical orthogonal carrier wave in time division manner in this case,it results in comparatively small overhead for the pilot transmission.

However, system (P-4) can not increase the spectral efficiency in thehigh data-rate transmission, because each symbol contains the guardsequence. And, the peak transmit-power of (M+1)² times as large as thatof a single symbol transmission system is required, because the eachuser transmitter transmits a symbol made by adding (M+1) pieces of thesymbol components. Therefore, in system (P-4), there is a problemconcerning an increase in power and spectral efficiency.

System (P-5) is a system performing user signal separation by allocatingWalsh functions W_(k)=(W_(k1),W_(k2), . . . W_(kn), . . . W_(kK))(k,n=1,2, . . . K) (respective rows of an Hadamard matrix with size ofK×K) with length K chips to K users as the spreading sequences, andutilizing 0-shift orthogonality between W_(k) and W_(k′)(k′≠k). Useru_(k) prepares a transmit-data of M bits as a binary sequence d_(k)(period T_(B)=MT_(C), T_(C): chip period) with M chips, as shown in FIG.19( a), and produces a guard added data-block d_(k) ^(g) (period T_(E))by appending a guard sequence g_(k) (period T_(g)=L_(g)T_(C)) which is acopy of the rear part of d_(k) and has L_(g) chips in length, todata-block d_(k).

A base-band transmit-signal is obtained by the following equations, whenobtaining a convolution product of the k-th spreading sequence and guardadded data-block d_(k) ^(g) (the figure is a case of K=4),

s_(k) ⁰=W_(k)

d_(k) ^(g)   (E-2)

where

shows Kronecker product, taking a convolution product (s_(kn)⁰=w_(kn)d_(k) ^(g), n: ordinal block number). A transmit-symbol s_(k) isproduced by modulating a common carrier wave f_(C) by signal s_(k) ⁰,and this symbol is transmitted. A base station receiver produces ademodulated symbol r by modulating a multiplexed received symbol bylocal carrier wave f_(C), as shown in FIG. 19( b). In the figure r₁ andr₂ which users u₁ and u₂ have transmitted, out of the components of r,are shown in a case where each component consists of 3 waves. Amultiplexed demodulated core-symbol r*⁰(r¹,r², . . . r^(K)) is extractedby removing hatched part r_(g) from a demodulated symbol r. A data-blocksoft output is obtained by the following equations, when multiplyingsymbol r*⁰ by spreading sequence W_(k).

$\begin{matrix}{\gamma_{k} = {\frac{1}{K}{\sum\limits_{n = 1}^{K}\; {r^{*}w_{kn}}}}} & \left( {E\text{-}3} \right)\end{matrix}$

The above equations indicate a mean value counted by averaging all ofγ_(k) ^(n) with respect to n, as illustrated. There is nointer-data-block interference, because the guard sequence is appended.Therefore, perfect user signal separation is achieved by theorthogonality of sequences in W_(k). Since inter-bit interference iscontained in a soft output vector γ_(k) with M chips, each of thetransmit-data can be detected by carrying out inter-bit interferenceseparation with system (P-2) and (P-3) using channel characteristicbetween a base station and each user.

However, the spectral efficiency considerably decreases, because guardsequence g_(k) must be appended to every data-block d_(k) in system(P-5), therefore an overhead factor ξ=L_(g)/M increases as the data rateincreases. In this case, when M is chosen to an abnormally large valuein order to make ξ small, user signal separation with Eq. (E-3) tends tobe difficult, because the channel characteristic changes during symbolperiod T_(P) by the Doppler shift.

And, when transmitting a scrambled transmit-symbol made by multiplyingeach transmit-symbol by a scrambling sequence in order to avoid theinter-cell interference, the orthogonality of W_(k) considerablydegrades according to the slight synchronous deviation among the userspecific received signal components which occurs in the up-linktransmission. Therefore, the user signal separation can not be achieved.

In addition, there is a problem such that providing multi-rate symboltransmission services with different data rates to all the users becomedifficult.

System (P-6) is a system where user u_(k) modulates a shift orthogonalsequence C_(k)(=c_(k1),c_(k2), . . . , c_(kN)) with length N as shown inFIG. 20( a) by data-block d_(k) consisting of M bits to produce amodulated output s_(k) ⁰, modulates a common carrier wave f_(C) byoutput s_(k) ⁰ to produce a transmit-symbol s_(k), and transmits thissymbol.

A base-station receiver produces a demodulated symbol r by demodulatinga multiplexed received symbol of which components have been incomingfrom K users in a synchronous condition with a local carrier wave. Bymultiplying this symbol r by a sequence for main wave C_(k) ^(M) whichis said orthogonal sequence C_(k) itself, and by another sequence fordelayed wave C_(k) ^(D) which is made by shifting sequence C_(k) by onechip toward right (and removing the last chip from C_(k)), respectively,a multiplied output is obtained as follows.

$\begin{matrix}\left. \begin{matrix}{\gamma_{k}^{D} = {C_{k}^{D}r}} \\{\gamma_{k}^{M} = {C_{k}^{M}r}}\end{matrix} \right\} & \left( {E\text{-}4} \right)\end{matrix}$

A correlated soft-output given by the following equation is obtained byaveraging the multiplied output, in a unit of the block, and theseoutputs are shown in FIG. 20( b).

$\begin{matrix}{\gamma_{k} = {\frac{1}{N}\left\{ {{\sum\limits_{n = 2}^{N}\; {c_{{kn} - 1}^{D}r_{n}}} + {\sum\limits_{n = 1}^{N - 1}\; {c_{kn}^{M}r_{n}}}} \right\}}} & \left( {E\text{-}5} \right)\end{matrix}$

Since user signal separation can be achieved due to the shiftorthogonality of sequence set C_(k) in this process, soft-output γ_(k)is composed of transmit-data component with M bits which u_(k) hastransmitted, and the delayed wave component. The transmit-data can bedetected by removing the inter-bit interference included in γ_(k) by thesame means as that explained with system (P-7).

However, since the family size of the shift orthogonal sequence is(N−1)/2, the user population which can be accommodated in system (P-6),is limited to

K≦(N−1)/2   (E-6)

In addition, there is a problem such that, this system does not have aninterference avoiding function against the inter-cell interference, andit is difficult to perform multi-rate transmission, while retaining theuser separating function within a cell.

In addition, there are problems such that this system does not have aninterference avoiding function against the inter-cell interferencesimilarly to system (P-7), and it is difficult to perform multi-ratetransmission, while retaining the user separating function within acell.

In system (P-7), M(L≧M≧1) kinds of spreading sequences c_(m)(m=1,2, . .. M) with a length of L chips are allocated to the k-th user, andmultiplexed spreading sequence {circumflex over (d)}_(k) with L chips(period T_(B)=LT_(C)) made by summing concurrently M pieces of modulatedoutputs {circumflex over (d)}_(km) such as to be obtained by modulatingthe m-th sequence c_(m) by the m-th transmit-data b_(km), as shown inFIG. 21( a). A repeated block Σ_(k) is produced by repeating thissequence {circumflex over (d)}_(k), K times, as a core-symbol (periodT_(S)=LKT_(C)). By appending a guard sequence g_(k) with L_(g) chips(period T_(g)=L_(g)T_(C)) to the core-symbol as shown in FIG. 21( b), aguard added multiplexed symbol Σ_(k) ^(g) with (L_(g)+LK) chips (periodT_(P)=(L_(g)+LK)T_(C)) is produced as a base-band transmit-symbol. Whena receiver receives this signal, the core-part over period T_(S) (LKchips) is extracted as a core-symbol. This core-symbol becomes a signalmade by K times repeating an identical component, if a sum of the delaytime due to the multi-paths in transmission and inter-user timingdeviation at the receiver is less than L_(g) chips.

Since this core-symbol has a comb-form spectrum, if producing atransmit-symbol s_(k) by modulating a carrier wave of differentorthogonal frequency f_(k) beforehand allocated to each user abovestated symbol s_(k) ⁰ and transmitting it, the receiver can obtain ademodulated symbol such as not to contain components of the other usersby demodulating a multiplexed received symbol with f_(k). Namely,perfect user signal separation is performed. Since the demodulated anduser signal separated output vector can be further separated intorespective of M pieces of sequence components, using M pieces of thespreading sequences and channel characteristics which the receiverproduced in advance, by the method of systems (P-2) and (P-3), M piecesof the transmit-data can be detected.

However, since each transmitter of system (P-7) makes thetransmit-symbol of a multiplexed sequence made by summing concurrently Mpieces of spreading sequences in chip-wise, the peak-transmit-powerbecomes M² times larger than that of a system transmitting one piece ofspreading sequence. There is a problem that an increase in the requiredpower brings a larger cost of the system.

In addition, intra-cell user separation function is lost according toslight synchronous deviation of the user signals in the up-linktransmission, when a transmit-symbol which is additionally multiplied bya scrambling sequence is used, in order to prevent inter-cellinterference. And, the user separating function is also lost forinter-block interference due to the delayed waves in the down-linktransmission, when the scramble sequence is used. There is an additionalproblem such that this system does not have means to perform multi-ratetransmission, while retaining said user separating function.

DISCLOSURE OF THE INVENTION

This invention was made to solve the following issues, by offeringdesign techniques for new multi-user transceivers. These issues includesolving of imperfect user signal separation function which theinterference canceller in system (P-1) indicates, avoiding of thespectral efficiency reduction due to guard sequence appended symbols,each carrying 1 bit, which are employed by de correlation circuitdetection in system (P-2), multi-user CDMA with MMSE detection in system(P-3) or repeated sequence multiplexing modulation in system (P-4),avoiding of an increase in guard overhead caused by guard sequencesappended to data-block-wise to a data-block-repetition-symbol used insystem (P-5), avoiding of efficiency reduction caused by theuser-restriction in system (P-6) which is allowed to accommodate alimited number of users less than a half of the spreading factor,because of using shift orthogonal spreading sequences, avoiding of anincrease in transmit-power in system (P-7) using symbols composed ofrepetition of multiple spreading sequences.

Namely this invention was performed to construct systems which canachieve technical objectives characterized by providing anti-inter-cellintra-cell interference function or multi-rate transmission functionwhich conventional systems have not provided.

In addition, this invention was made to solve a problem such thatinsufficient improvement in the soft-output SN ratio of conventionalMIMO systems or adaptive array systems using multiple receive-antennae,and to establish optimization technology for improving the soft-outputSN ratio by utilizing the surplus dimensions included in multiplexedreceived-symbols.

In order to solve the above-described problems, the invention claimed inclaim 1 of the present invention is a data-block spread spectrumcommunications system, wherein a transmitter of each of the userstations comprises means for producing a block spread transmit-symbol byapplying user specific spectral spreading processing and carrier wavemodulation to a transmit data-block which is composed of a time sequenceof plural transmit-data, and transmitting said transmit-symbol, and areceiver comprises means for receiving multiple of said transmit-symbolswhich all the users have transmitted by said means as a multiplexedreceived symbol, and performing all the user signal separation andseparation of respective data contained in said transmitted data-blocks,using a knowledge of channel characteristics between said transmittersand said receiver beforehand acquired, said user specific spectralspreading processing and carrier wave modulation, characterized by thata transmitter of the k-th user comprises, means for producing a blockspread symbol by modulating the k-th orthogonal carrier wave f_(k) by aguard added data-block repeated sequence which is made by appending aguard sequence to a data-block repeated as a transmit-symbol, and saidreceiver comprises, means for producing a demodulated output bydemodulating said multiplexed received symbol by the k-th orthogonalcarrier wave f_(k), applying averaging operation in an unit of thedata-block to a demodulated core-symbol on the core symbol period whichis made by removing a guard part of said demodulated output to produce ade-spread data-block corresponding to the data-block which the k-th userhas transmitted, by removing the other user signal components, anddetecting respective of said transmit-data by making on the harddecisions soft outputs which is obtained by separating respective ofsaid transmit-data components, using said de-spread data-block and saidchannel characteristics.

The invention claimed in claim 2 of the present invention is adata-block spread spectrum communications system, wherein in said systema transmitter of each user comprises means for producing a block spreadsymbol by spreading a transmit data-block which is composed of a timesequence of plural transmit-data with a spreading sequence allocated tosaid user, and transmitting said block spread symbol using a commoncarrier wave as a transmit-symbol, and a receiver comprises means forreceiving multiple transmit-symbols which all the users have similarlytransmitted as a multiplexed received symbol, and performing separationof all the user symbols with said spreading sequence and separation ofindividual transmit-data contained in said symbol, characterized by thata transmitter of the k-th user comprises, means for producing a guardadded block spread symbol by appending a guard sequence to a data blockspread symbol which is made with the k-th spreading sequence Z_(k)belonging to a zero-correlation-zone sequence-set as said spreadingsequence, and producing a transmit-symbol by modulating said carrierwave by said guard added block spread symbol, and a receiver comprisesmeans for producing a demodulated output by demodulating saidmultiplexed received symbol by said carrier wave, producing ademodulated core-symbol by removing a guard part from said demodulatedoutput and producing separately a de-spread data-block corresponding toa data-block the k-th user has transmitted by removing the other users'signal components by a method of applying said demodulated core-symbolto a matched filter so as to de-spread said demodulated core-symbol andto average a resultant output, and means for producing a soft-outputvector consisting of respective transmit-data, each is separated fromthe other data component, corresponding to said transmit-data-blockusing said de-spread data-block and said channel characteristic, anddetecting respective of said transmit-data by making it on the harddecisions said soft-output vector.

The invention claimed in claim 3 of the present invention is adata-block spread spectrum communications system according to claim 2,characterized by that said system comprises means for allocating a zerocorrelation zone sequence Z_(k) ⁰ and a sequence Z_(k) ¹ which is madeby shifting sequence Z_(k) ⁰ by 1 chip cyclically to the left to usersu_(k) ⁰ and u_(k) ¹, respectively, and a transmitter of each usercomprises means for producing each transmit-symbol by making aconvolution product of said sequence and a transmit-data-block, and areceiver comprises, means for producing respective de-spread data-blocksby de-spreading said multiplexed demodulated symbol by respective ofsaid sequences to make de-spread outputs, and applying averagingprocessing to the de-spread outputs, respectively, means for producing asystem of de-correlating equations using three elements, those are aconcatenated data-block made by concatenating said data-blocks, anunknown vector made by concatenating said transmit-data-blocks and achannel matrix made by said channel characteristics between respectiveusers and the receiver, and means for detecting data by making on harddecisions each component of a soft output vector obtained by solvingsaid system of de-correlating equations, producing a reproduced signalwhich contains received symbol components received from all the usersusing sequences Z_(k) ⁰(k=1,2, . . . K), and applying repeatedly saidde-spreading processing with sequence Z_(k) ¹ to a signal which is madeby removing said reproduced signal from said multiplexed receivedsymbol, and thereby composing a system such that 2 users cansimultaneously transmit transmit-symbols using one of said zerocorrelation zone sequences.

The invention claimed in claim 4 of the present invention is adata-block spread spectrum communications system, according to claim 1to perform multiple data-rate transmission, characterized by that saidtransmitter of the k-th user comprises, means for producing a guardadded symbol by appending a guard sequence to an output which is made byrepeating N times a data-block of a length M, and a transmitter of thek′-th user comprises, means for producing another guard added symbol ofwhich transmission data-rate is different each other by appending aguard sequence to an output which is made by repeating Nn times adata-block of a length M/n, and respective user transmitters comprise,means for producing transmit-symbols by modulating the k-th and thek′-th orthogonal carrier waves by said guard added symbols,respectively, and said receiver comprises, means for producingseparately de-spread data-blocks corresponding to the respective user'stransmit-symbols by modulating a received core-symbol which is made byremoving the guard part from said multiplexed received symbol byrespective of the k-th and the k′-th orthogonal carrier waves.

The invention claimed in claim 5 of the present invention is adata-block spread spectrum communications system, according to claims 2and 3 to perform multiple data-rate transmission, characterized by thatsaid transceiver system comprises, means for preparing spreading layerswith N hierarchical layers such as composed of sequence sets Z^(n)=(Z₁^(n),Z₂ ^(n), . . . , Z_(k) ^(n), . . . Z_(Kn) ^(n)) consisting of K_(n)pieces of zero correlation zone sequences as the elements of the n-thlayer, in advance, and a base station comprises, means for allocatingsequences belonging to one or multiple spreading layers corresponding totransmit-data rates to each user, and each user's transmitter comprisesmeans for producing a base-band multistage block spread symbol by amethod of spreading a transmit-data-block by making sequentiallyconvolution products of these sequences allocated and said data-block,and transmitting an output which is made by modulating a carrier wave bya guard added symbol made by appending a guard sequence to each of saidmulti-stage block spread symbols, and said receiver comprises, means forproducing said demodulated core symbol by demodulating said multiplexedreceived symbol by the carrier wave, and separately producing each ofde-spread data-blocks such as not to contain the other transmit-symbolcomponents de-spread by different zero correlation zone sequences, byde-spreading, in an unit of the data block, said core-symbol with saidspreading sequences which each transmitter has used as said spreadinglayers.

The invention claimed in claim 6 of the present invention is adata-block spread spectrum communications system, according to claims 1and 4, characterized by that each of the user transmitters of thek(=1,2, . . . K)-th user group in a system, of which users are dividedby K user groups, each user group having plurality Q of users,comprises, means for modulating the k-th orthogonal carrier wave f_(k)by said guard added data-block repeated sequence, and said receiverequipped with multiple receive-antennas with antenna ordinal numbere(=1,2, . . . E) comprises, means for producing a demodulated symbol bymodulating a multiplexed received symbol which has received via e-thantenna with the k-th orthogonal carrier wave f_(k), and separatelyproducing a multiplexed de-spread data-block corresponding todata-blocks which the k-th user group has transmitted, by applying theaveraging operation to a demodulated core symbol made by removing theguard part from said demodulated symbol, to remove signal components ofthe other user groups, means for producing a concatenated de-spreadvector by concatenating E pieces of said multiplexed de-spreaddata-blocks, and producing a soft output vector by solving a system oflinear equations with multiple unknowns, composed of an extended channelmatrix which is made of Q times E pieces of the channel characteristicsbetween respective users of the k-th user group and thereceive-antennas, said concatenated de-spread vector, and an unknownvector corresponding to the transmit-data of the Q users, and means forobtaining transmit-data of the respective users belonging to saidrespective groups by making it on the hard decisions respectivecomponents of said soft output vector.

The invention claimed in claim 7 of the present invention is adata-block spread spectrum communications system, according to claims 2,3 and 5, characterized by that said transmitter of the k(=1,2, . . .K)-th user group in a system, of which users are divided by plural usergroups, each user group having plurality Q of users, comprises, meansfor producing a data-block spreading sequence using the k-th spreadingsequence Z_(k) belonging to said zero correlation zone sequence set, andsaid receiver equipped with multiple receive-antennas with antennaordinal number e(=1,2, . . . E) comprises, means for producing ademodulated output by demodulating the e-th multiplexed received symbolwith said carrier wave, separately producing a multiplexed de-spreadvector corresponding to data-block s which the k-th user group hastransmitted, by applying de-spreading operation to a demodulated coresymbol made by removing the guard part from said demodulated output withsaid spreading sequence Z_(k) to produce de-spread output, and applyingthe averaging operation to said de-spread output to remove signalcomponents of the other user groups, and means for producing aconcatenated de-spread vector by concatenating E pieces of saidmultiplexed de-spread vector, producing a soft output vector by solvinga system of linear equations with multiple unknowns, composed of anextended channel matrix which is made of Q times E pieces of the channelcharacteristics between respective users of the k-th user group and thereceive-antennas, said concatenated de-spread vector, and an unknownvector corresponding to the transmit-data of the Q users and, obtainingtransmit-data of the respective users belonging to said respectivegroups by making it on the hard decisions respective components of saidsoft output vector.

The invention claimed in claim 8 of the present invention is adata-block spread spectrum communications system, according to claims 1to 7, characterized by that said transmitter belonging to each cellcomprises, means for producing said data-block repeated sequence or saiddata-block spread symbol over a cell specific transmit-core-blockspreading period which is allocated to said cell beforehand, producing atransmit-symbol by modulating the carrier wave described in claims 1 to6 by a base-band guard added symbol made by appending a guard sequenceto said core symbol, and transmitting said transmit-symbol, and saidreceiver comprises, means for producing a demodulated core-symbol on areceived timing synchronized with said cell specific transmit-core blockspreading period using said multiplexed received symbol and said carrierwave which the transmitter has used, and thereby producing a de-spreaddata-block with suppressed inter-cell interfering components, byapplying the same processing to said demodulated core-symbol as themethod described in claims 1 to 6.

The invention claimed in claim 9 of the present invention is adata-block spread spectrum communications system, according to claims 1to 7, characterized by that said transmitter belonging to each cellcomprises, means for producing a guard added data-block repeatedsequence or a guard added data-block spread symbol using a cell specificchip rate made by summing a chip rate bias which is allocated to saidcell beforehand to a nominal chip rate, producing a transmit-symbol bymodulating one of said carrier waves described in claims 1 to 6, andtransmitting said transmit-symbol, and said receiver comprises, meansfor producing a correlation output between a multiplexed demodulatedsymbol with continuous waveform which has been produced using saidcarrier wave and a chip waveform on said cell specific chip rate,producing a discrete time sequence having the amplitude of saidcorrelation output as a demodulated core symbol, and applying saidaveraging processing to an output made by de-spreading said demodulatedcore-symbol by the method described in claims 1 to 6, to produce ade-spread data-block where an inter-cell interfering component issuppressed.

The invention claimed in claim 10 of the present invention is adata-block spread spectrum communications system according to claims 2,3, 4 and 7, characterized by that said system allocates one or pluralcell specific zero correlation zone sequence sets as spreading sequencesets to each cell in which a cross correlation value between spreadingsequences chosen from two spreading sequence sets belonging to anidentical one of said spreading layers allocated to adjacent two cellstakes small value.

The invention claimed in claim 11 of the present invention is adata-block spread spectrum communications system, according to claims 1and 2, characterized by that each of said transmitters comprises, meansfor producing a transmit-symbol by substituting a pilot sequence foreach of said transmit-data-blocks according to claims 1 and 2 as a pilotsymbol, and transmitting said pilot symbol over a cell common pilot timeslot, and said receiver comprises, means for producing a demodulatedpilot response by demodulating, de-spreading and applying averagingprocessing to a multiplexed received pilot symbol extracted by themethod described in claims 1 and 2, and obtaining a channelcharacteristic based on a correlation output between j(=0,1,2, . . . ,J−1) shift analyzing sequence a_(j) of an analyzing sequence orthogonalto said pilot sequence except at 0 shift position and said demodulatedpilot response.

The invention claimed in claim 12 of the present invention is adata-block spread spectrum communications system, according to claim 11,characterized by that said transmitter comprises, means for preparing apilot set consisting of multiple (N_(p)) pieces of pilot sequences ofwhich frequency spectra complement each other, producing N_(p) pieces ofpilot symbols by such a method that each of them is constructed using apilot sequence selected out of said pilot sequence set as atransmit-pilot symbol, and transmitting sequentially these N_(p) piecesof transmit-pilot symbols, and an receiver comprises, means forpreparing an analyzing sequence orthogonal to each of said pilotsequences except at the 0 shift position, obtaining N_(p) pieces ofchannel characteristics using respective of received pilot symbols andsaid corresponding analyzing sequences, and producing a precise pilotresponse by taking a mean value of these N_(p) pieces of channelcharacteristics as a pilot characteristic.

The invention claimed in claim 13 of the present invention is adata-block spread spectrum communications system, according to claims 6and 7, characterized by that said receiver comprises, means forproducing a de-spread matrix X_(k) using E pieces of said de-spreaddata-block γ_(k) ^(e)(e=1,2, . . . , E) addressed to the k-th user whichhas been produced with the e-th receive-antenna output, and producing atransformed matrix Y_(k) by multiplying said de-spread matrix by such anorthogonal transform matrix Ω_(k) that autocorrelation matrix of saidtransformed matrix may be diagonalized, means for selecting a weightingcorresponding to the eigen value of said transformed matrix for the e-thtransformed component y_(k) ^(e), obtaining a soft output vector {tildeover (d)}_(k) ^(e) corresponding to said component y_(k) ^(e) by amethod of solving a system of multiple linear equations, and means forproducing a detected data vector {circumflex over (d)}_(k) correspondingto said transmit-symbol by making it on the hard decisions an outputvector which is made by summing some of said soft output vectors, eachis multiplied by said weighting.

The invention claimed in claim 14 of the present invention is adata-block spread spectrum communications system, according to claim 13,characterized by that said receiver comprises, means for producing atransformed matrix W_(k) by applying orthogonal transform to a de-spreadmatrix Γ_(k) consisting of L pieces of de-spread data-block γ_(k) ^(l)which has been produced with a symbol on the l(=1,2, . . . , L)-th timeposition by the method described in claims 6 and 7 with such anorthogonal transform matrix A_(k) that an autocorrelation matrix oftransformed matrix W_(k) may be diagonalized, and selecting for a softoutput vector w_(k) ^(l) of said transformed matrix W_(k), and aweighting corresponding to the l-th eigen-value of transformed matrixW_(k), and means for producing a detected data of the k-th user using anoutput vector made by summing some of soft output vectors w_(k) ^(l)each is multiplied by said weighting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is propagation path model of transmission waves in a CDMA mobilecommunications system, and Fig. (a) shows intra-cell up-link paths, Fig.(b) shows intra-cell down link paths and Fig. (c) shows inter-cellinterfering waves.

FIGS. 2( a)˜(c) are time-charts of basic transmit and receiveddata-block symbols.

FIGS. 3( a) and (b) are time-charts of transmit- and received symbols ofa repeated data-block carrier wave modulation system.

FIGS. 4( a) and (b) are illustrations of comb-form spectra showing theprinciple of frequency division transmission.

FIG. 5 is a block diagram of a base station transmitter [TX(BS)].

FIG. 6 is a block diagram of the k-th user receiver [RX(u_(k))].

FIGS. 7( a)˜(c) are illustrations showing symbol composition andfrequency spectrum of multi-rate transmit-signals.

FIGS. 8( a) and (b) are block diagrams of a user group transmissionsystem using an identical carrier wave.

FIG. 9 is a transmit-symbol time-chart used for a cell correspondentblock-spread core symbol period allocation system.

FIG. 10 is a transmit-symbol time-chart used for a cell correspondentchip rate allocation system.

FIGS. 11( a) and (b) are symbol frame time-charts used for a pilottransmission.

FIGS. 12( a)˜(c) are time-charts of transmit- and received symbols of azero correlation zone sequence modulation system.

FIGS. 13( a) and (b) are block diagrams of the k-th user transceiver.

FIGS. 14( a) and (b) are time-charts of transmit and received symbols ofthe multistage data-block spreading system using zero correlation zonesequences.

FIGS. 15( a) and (b) are block diagrams of user group transmissionsystem using an identical spreading sequence.

FIG. 16 is a functional block diagram showing transceiver of aconventional CDMA communications system.

FIG. 17 is a functional block diagram showing conventional multi-userreceiver (interference canceller system).

FIGS. 18( a) and (b) are functional block diagrams showing conventionalmulti-user receivers (systems of de-correlating equations), where Fig.(a) shows de-correlating detector (DD) and Fig. (b) shows minimum meansquare error detector (MMSE-D).

FIGS. 19( a)˜(c) are time-charts of transmit- and received signals ofconventional data-block spreading system using Walsh functions.

FIGS. 20( a) and (b) are time-charts of transmit- and received signalsof a conventional data-block spread system using shift orthogonalsequence.

FIGS. 21( a) and (b) are time-charts of transmit-symbol of aconventional multiplexed spread symbol repeating system using carrierwave modulation.

BEST MODE FOR CARRYING OUT THE INVENTION

This invention provides CDMA systems which overcome the above-mentionedproblems such that conventional CDMA systems are vulnerable to theinterference disturbance due to the other mobile stations (users), andraise the spectral efficiency.

A. Repeated Data-Block Modulated Orthogonal Carrier Wave System A-1.Basic System.

FIG. 1 is a supplementary drawing for all embodiment examples of thisinvention, where intra-cell transmission routes of a CDMA mobilecommunications system are illustrated. FIG. 1( a) shows the paths ofup-link transmission via which a mobile station u_(k)(k=1,2, . . . K)(called hereafter user) in a cell transmits a transmit-symbols_(U)(u_(k)) to the base station (BS) in this cell. Now, let the firstuser u₁ be a desired user (the following part is explained under thisassumption). A direct wave of a received symbol r_(D) is a desired wave,while the dotted lines show here the delayed waves generated by themulti-path. Delayed waves which the transmit-symbol of the desired userhas generated become auto-interference waves. On the other hand,transmit-waves sent out from the users (can be called interferenceusers) other than the desired user are received as inter-userinterference. In these waves, not only direct wave but also delayedwaves, as illustrated, due to multi-paths are included. Therefore,received interference waves are the sum of the auto-interference wavesand the inter-station interference waves.

All received waves are expressed in the following equations,

$\begin{matrix}\left. \begin{matrix}{r = {r_{D} + r_{I} + x}} \\{r_{I} = {r_{SI} + r_{XI}}}\end{matrix} \right\} & (1)\end{matrix}$

where x is a white noise. (AWGN: Additive White Gaussian Noise,generally AWGN is shown by x in the following part.) In FIG. 1( a), areceived wave component received at a base station BS from the useru_(k) is denoted by r_(k). The received wave r₁ illustrated of thedesired user is equivalent to r₁=r_(D)+r_(SI) in Eq. (1).

FIG. 1( b) shows the paths of down link transmission. Delayed waves ofmulti-path waves take place also in this case, shown by the dottedlines. And, received wave r₁ which user (station) u₁ receives includesnot only the direct wave and the delayed waves corresponding to thetransmission of transmit-waves s_(D)(u₁) illustrated, but also thedirect wave and the delayed waves based on transmission wavess_(D)(u_(k))(k≠1) to the other users u_(k) (k≠1).

Therefore, the transmitter of base station BS has the almost samefunction as those of the transmitters of all the users in FIG. 1( a),and transmit-signal s_(D)(u₁˜u_(K)) is given by a sum of transmitoutputs addressed to all the users.

FIG. 1( c) is a diagram showing the paths of inter-cell interferingwaves among 3 cells C₁, C₂ and C₃. The receiver of a base station BS¹ ofa cell C₁ receives interference due to the up-link transmission pathsshown by solid lines coming from users u_(k) ² and u_(k) ³ belonging tocells C₂ and C₃, respectively. And, the receiver of user u_(k) ¹ of cellC₁ receives interference due to the down link transmission paths shownby the dotted lines coming from base stations BS² and BS³ of cells C₂and C₃ respectively.

In this invention, the transmitter of a base station BS transmits usercommon pilot symbols to the k(=1,2, . . . K)-th user u_(k) via a downlink, and u_(k) estimates the channel (gain) characteristic from BS tou_(k) using received response of pilot symbols. The BS transmitterconverts M bit binary data d_(k)=(b_(k1),b_(k2), . . . b_(km), . . .b_(kM)) to transmit to u_(k) into a data-block (unit) d_(k). A guardadded symbol Σ_(k) ^(g) is made by appending a guard sequence to acore-symbol which is made, by repeating N times this data-block. Anoutput made by modulating the k-th carrier wave f_(k) by symbol Σ_(k)^(g) is sent out with similar data symbols of the other users.

The receiver of user u_(k) receives a multiplexed received symbol inwhich all of user specific received symbol components have beenmultiplexed, and produces a demodulated data-block {tilde over (d)}_(k)which is obtained by applying the k-th carrier-wave f_(k) to themultiplexed received symbol, and thereby separating respective userspecific components with following averaging operation. The receiverobtains a soft-output {tilde over (b)}_(km) corresponding to the m-thdata b_(km) included in data-block by removing inter-bit interferencebetween bits b_(km) and b_(km′) (m′≠m) included in {tilde over (d)}_(k)using a correlation matrix H_(k) made of the channel characteristics.

Thus the receiver obtains a detected binary data-block {circumflex over(d)}_(k) as a vector consisting of M bit data with a method such as tomake hard decisions on respective soft-outputs {tilde over (b)}_(km)corresponding to the m-th transmit-data to the k-th user b_(km). This isa system which can transmit information of M bits per block-symbol, andit has a feature such as to enhance the spectral efficiency due tosaving of the guard sequence.

For up-link transmission, a transmitter of the k-th user u_(k) producespilot and data symbols by the same method as that for the down linktransmission, and transmits them to base station BS. The receiver of BSdetects a data-block which transmitter of user u_(k) has transmittedusing the same method as that the receiver of u_(k) uses.

FIGS. 2, 3 and 4 are supplementary explaining drawings of the firstembodiment of this invention, showing time composition and spectralcharacteristics of data-block symbols which are produced at thetransceivers. d_(k) in FIG. 2( a) shows a data-block which consists of abinary data sequence of M bits to be transmitted by the k-th user u_(k),and given by,

$\begin{matrix}{d_{k} = {\left( {b_{k_{1}},b_{k_{2}},{\ldots \mspace{14mu} b_{k_{m}}},{\ldots \mspace{14mu} b_{k_{M}}}} \right) = {\sum\limits_{m = 1}^{M}\; {b_{k\; m}{\delta \left( {t - {mT}_{C}} \right)}}}}} & (2)\end{matrix}$

where T_(C) and δ are chip period, and delta function, respectively.T_(B)=MT_(C) illustrated is a data-block period.

FIG. 2( b) shows a data-block sequence specified by a sequential blockordinal number n(0,1,2, . . . N). Σ_(k) given by the following equation,is a core-block sequence (core-symbol) with length L=MN (in chips) madeby N pieces of repeated data-blocks as illustrated,

Σ_(k)=w

d_(k)   (3)

where w is a spreading sequence with N chips in length, giving arepeating pattern of d_(k) [Note, a periodic sequence such as (1, −1, 1,−1, . . . ) or (1, 1, −1, −1, 1, 1, −1, −1, . . . ) can be used, becauseorthogonal relation can be kept with such a sequence, as explained laterwith FIG. 4.],

indicates Kronecker product.

Σ_(k) ^(g) illustrated in the figure is a guard added data-blockrepeated sequence which is made by appending a guard sequence g_(k) withlength L_(g) to the header part (n=0) of core-symbol Σ_(k), and it iscalled a guard added symbol. In FIG. 2( b), T_(P) is guard added blockspreading period (guard added symbol period) and T_(S) is core blockspreading period (core-symbol period) which is a time duration made byremoving guard period T_(g) from T_(P).

Guard sequence g_(k) is a cyclic prefix composed of the rear part withL_(g) chips of Σ_(k). Σ_(k) ^(g) is a sequence consisting ofL_(E)=(MN+L_(g)) chips, and it is given by the following equations, bydenoting respective chips by σ_(k1),

$\begin{matrix}{\Sigma_{k}^{g} = {\left( {\sigma_{k\; 1},\sigma_{k\; 2},{\ldots \mspace{14mu} \sigma_{k,_{{MN} + L_{g}}}}} \right) = {T_{CP}\left\lbrack {w \otimes d_{k}} \right\rbrack}}} & (4) \\{T_{CP} = \left( \frac{\left. O_{{Lg} \times {({{NM} - {Lg}})}} \middle| I_{Lg} \right.}{I_{NM}} \right)} & (5)\end{matrix}$

where T_(CP) is a guard appending operator that is a cyclic sequencegeneration matrix having a function of appending a guard sequence sothat Σ_(k) ^(g) may become a cyclic sequence, O_(a×b) is a matrix with asize of a×b composed of an element “0”, and I_(a) is an identity matrixwith a size of a×a.

Guard added symbol Σ_(k) ^(g) is an impulse train signal on a discretetime axis such that each of the impulses arranged in chip period (T_(C))spacing has a chip-amplitude-value σ_(k1). It is necessary to replaceeach of the chips with a chip wave-form q having a limited bandwidth inorder to make it to be a base-band-signal for transmission. A guardadded symbol having a continuous wave-form is given by the followingequation by making a convolution product of Σ_(k) ^(g) and q.

{tilde over (Σ)}_(k) ^(g)=Σ_(k) ^(g)

q   (6)

s_(k) in FIG. 2( b) is a transmit-signal (“signal means a block spreadsymbol, and it may be expressed by BSS hereafter”) given by thefollowing equation which is made by modulating a carrier wave of thek-th frequency f_(k) allocated to the k-th user u_(k) by guard addedsymbol Σ_(k) ^(g),

s_(k)={tilde over (Σ)}_(k) ^(g)√{square root over (2P_(S))} cos 2πf_(k)t  (7)

where P_(S) is transmit-power (P_(S)=1 W is assumed hereafter).

The carrier waves allocated to respective users have an orthogonalrelation given by the following equations, for the purpose of usersignal separation,

f _(k) =f ₀ +kf _(S) (k=1,2, . . . K)   (8)

f _(S) =T _(S) ⁻¹=(NMT _(C))⁻¹   (9)

where f₀, f_(S) and kf_(S) are a reference carrier frequency, afundamental carrier frequency given by the reciprocal of core-symbolperiod T_(S), and an intermediate frequency to discriminate respectivesignals of users u_(k). (Such a method is generally used in actualequipment, that a base-band-symbol modulates frequency kf_(S) at thefirst stage, and the resultant output modulates a frequency f₀ which isfar higher than kf_(S) at the next stage.)

Now, let's explain FIG. 2( c). r is a multiplexed received symbol, inwhich K pieces of the k-th received symbol component r_(k) (BSS) havebeen multiplexed. Symbol component r_(k) is a signal which has arrivedat a receiver so that the k-th transmit-symbol s_(k) transmitted by useru_(k) arrives at the receiver, on a synchronous (down-link) or aquasi-synchronous (up-link) condition with those transmitted by theother users.

It is here assumed that a channel characteristic to the k-th user u_(k)from the base station is given by an impulse response of the followingequation, because the time resolution is given by the chip period,

h _(k)=(h _(k0) ,h _(k1) , . . . h _(kj) , . . . h _(k,J−1))^(T)   (10)

where h_(kj) is a complex amplitude component which delays from thedirect wave component h_(k0) by jT_(C). (for the down-link, responseh_(k) becomes identical for all the users). Therefore, a multiplexedreceived symbol in which the k-th received symbol component and theother similar user specific received symbol components have beenmultiplexed is given by the following equations, if denoting a timevariable and an AWGN component by t and x respectively.

$\begin{matrix}\left. \begin{matrix}{{r(t)} = {{\sum{r_{k}(t)}} + {x(t)}}} \\{{\sum{r_{k}(t)}} = {{\sum\limits_{j = 0}^{J - 1}\; {h_{jk}{s_{k}\left( {t - {jT}_{C}} \right)}}} + {x(t)}}}\end{matrix} \right\} & (11)\end{matrix}$

Multiplexed received symbol r consists of a guard sequence part r^(g)and a multiplexed received core-symbol which is the core-symbol-partover a core-period T_(S) as shown in the figure. The k-th user specificcomponent of r* is denoted by r*_(k)(=r_(k) ¹,r_(k) ², . . . , r^(n), .. . r_(k) ^(N)). (The display of time variable t is omitted hereafter.)r_(k) (h_(kj)) is a received symbol component having the j-th delayedwave amplitude shown in Eq. (10). A hatched part of the first block iscomposed of products of three elements which are transmit-data-blockd_(k), delayed wave amplitude h_(kj) and an operator D_(j) showingcyclical delay by jT_(C)(T_(C): chip interval). r_(k)(h_(k))=h_(k)d_(k)in FIG. 2( c) is a sum of these products with respect to j(=0,1,2, . . ., J−1).

Then, let's describe a principle of user (signal) separation. Ademodulated base-band core-symbol γ*_(k) ⁰=(γ_(k) ¹,γ_(k) ², . . . ,γ_(k) ^(N)) is obtained on period T_(S) by the following equation, whenperforming demodulation processing, such that a multiplexedreceive-core-symbol r*, shown in FIG. 2, is multiplied by carrier wavef_(k), and then only the low-frequency-component of the output less thana chip frequency f_(ch)(=T_(c) ⁻¹) is extracted with a filter,

$\begin{matrix}\left. \begin{matrix}{\gamma_{k}^{*0} = {\left\lbrack {\left\{ {{\sum\limits_{k = 1}^{K}\; {\sum\limits_{j = 0}^{J - 1}\; {\left( {h_{kj}\sum\limits_{k}} \right)D_{j}\sqrt{2}\cos \; 2\pi \; f_{k}t}}} + {x(t)}} \right\} \cos \; 2\; \pi \; {f_{k}(t)}} \right\rbrack \left( {f \leq f_{ch}} \right)}} \\{= {\sum\limits_{j = 0}^{J - 1}\; {\left( {h_{kj}\sum\limits_{k}} \right){D_{j}\left( {1 + {\cos \; 4\; \pi \; f_{s}t}} \right)}}}} \\{{+ {\sum\limits_{\underset{k^{\prime} \neq k}{k^{\prime} = 1}}^{K}\; {\sum\limits_{j = 0}^{J - 1}\; {\left( {h_{k^{\prime}j}\sum\limits_{k^{\prime}}} \right)\left\{ {{\cos \; 2\; {\pi \left( {k - k^{\prime}} \right)}f_{s}t} + {\cos \; 2\; {\pi \left( {k + k^{\prime}} \right)}f_{s}t}} \right\}}}}} + {x(t)}}\end{matrix} \right\} & (12)\end{matrix}$

where, D_(j) is a delay operator with jT_(C).

The demodulated output stated above is composed of N pieces ofdemodulated block-components γ_(k) ^(n)(n=1,2, . . . , N), each is onblock period T_(B), as shown in FIG. 2( c). γ*_(k) ⁰ can be convertedhere into the form of a vector composed of LM chips with chip periodspacing T_(C), by taking correlation output on every chip period T_(C)between the chip waveform in Eq. (6) and this demodulated output. Whenapplying averaging processing to this demodulated vector γ*_(k) ⁰, in anunit of data-block period (T_(B)), over one period T_(S) of fundamentalfrequency f_(S), the terms with a cosine wave take 0.

As a result, a demodulated data-block of the following equation isobtained as de-spread output γ_(k).

$\begin{matrix}{\gamma_{k} = {{\frac{1}{N}{\sum\limits_{n = 1}^{N}\; \gamma_{k}^{n}}} = {{\sum\limits_{j = 0}^{J - 1}\; {h_{1j}d_{k}D_{j}}} + x}}} & (13)\end{matrix}$

Thus, by averaging the output which is made by multiplying generallysymbol r* by carrier wave f_(k), the user components other than u_(k)are removed by this averaging process, and resultantly de-spreaddata-block γ_(k) of the k-th user is obtained as an user signalseparated output consisting of M chips. That is to say, the user signalseparation is performed.

This de-spread data-block γ_(k) contains delayed wave components(h_(kj)d_(k)D_(j), j≠0) due to the multi-paths, as it was shown in Eq.(13). These components are equivalent to those of inter-bit interferencecontained in the de-spread components. In order to remove them, it isrequired to solve a system of de-correlating equations given by thefollowing equations,

$\begin{matrix}\left. \begin{matrix}{\gamma = {{Hd} + x}} \\{\begin{pmatrix}\gamma_{1} \\\gamma_{2} \\\vdots \\\vdots \\\vdots \\\vdots \\\gamma_{M}\end{pmatrix} = {{\begin{pmatrix}h_{0} & \; & \; & \; & 0 & h_{2} & h_{1} \\h_{1} & h_{0} & \; & \; & \; & \vdots & \vdots \\\vdots & h_{1} & \ddots & h_{0} & \; & h_{J - 1} & \vdots \\h_{J - 1} & \vdots & \; & h_{1} & \ddots & \; & h_{J - 1} \\\; & h_{J - 1} & \; & \vdots & \; & h_{0} & \; \\\; & 0 & \; & h_{J - 1} & \; & h_{1} & h_{0}\end{pmatrix}\begin{pmatrix}b_{1} \\b_{2} \\\vdots \\\vdots \\\vdots \\\vdots \\b_{M}\end{pmatrix}} + \begin{pmatrix}x_{1} \\x_{2} \\\vdots \\\vdots \\\vdots \\\vdots \\x_{M}\end{pmatrix}}}\end{matrix} \right\} & (14)\end{matrix}$

where subscript component k indicating the k-th user is omitted forsimplicity; and H, d=(b₁,b₂, . . . , b_(m), . . . , b_(M))^(T) andx=(x₁,x₂, . . . , x_(M))^(T) are a channel response matrix consisting ofthe channel characteristic in Eq. (10) as the element, thetransmit-data-vector block in Eq. (2), and an AWGN component,respectively. It is possible to obtain a soft-output vector {tilde over(d)} as a solution vector of an unknown data-vector d by solving Eq.(14), with a de-correlating detector which multiplies γ by an inversematrix of H, or an MMSE detector which multiplies γ by a matrix H^(H)that is a conjugate transpose matrix of H, and additionally by(H^(H)H+N_(r0)I)⁻¹, the well-known means [refer to Eq. (45)] alreadyexplained with FIG. 18. By making hard decisions on the respectivecomponents {tilde over (b)}_(m) of soft-output-vector {tilde over (d)},a detected output {circumflex over (b)}_(m) of each transmit-data b_(m)can be obtained. That is to say, it is possible to obtain a detectedvector {circumflex over (d)}_(k) as represented by the followingexpression to which the subscript k is appended to indicate a vectorrelated to the k-th user u_(k).

{circumflex over (d)} _(k)=({circumflex over (b)} _(k1) ,{circumflexover (b)} _(k2) , . . . , {circumflex over (b)} _(km) , . . . ,{circumflex over (b)} _(KM))^(T)   (15)

FIG. 3 shows compositions of transmit- and received symbols of arepeated data-block orthogonal carrier-wave-modulation system which isthe first embodiment of this invention. Figure (a) showstransmit-symbols s_(k) (BSS) for 4 users u_(k)(k=1,2,3,4) which are madeby the method explained with FIG. 2. Preceding and succeeded parts ofrespective symbols are also shown in the figure. In this example, eachtransmit-symbol s_(k), corresponding to 4 users, is made by modulatingthe k-th carrier wave f_(k) by the k-th guard added data-block sequenceΣ_(k) ^(g) which is composed of 4 pieces of data-blocks and a guardsequence.

FIG. 3( b) shows the received symbol component r_(k) on the k-th carrierwave f_(k) and a multiplexed received symbol r (BSS) composed of 4components, which a receiver has received, when only transmit-symbolss_(k) shown in FIG. 3( a) have been transmitted. The figure is areceived symbol in case of J=3, and each user specific received symbolcomponent r_(k) consists of 3 waves. τ_(DM)[=(J−1)T_(C)] and τ_(a) inthe figure are the maximum delay time and arrival time difference of r₃compared to a reference arriving time of r₁. τ_(a) arises only inup-link so as to be generally τ_(a)≠0, because the received symbolcomponents asynchronously arrive. Now consider a method that abase-station controls each user's transmit-timing so that the maximumabsolute value of the arriving time deviation takes less than τ_(aM) asgiven by the following equations.

T _(g)>(τ_(aM)+τ_(DM))   (16)

This is called quasi-synchronous condition.

The other received symbol components are composed in the same way asthat described above, and each of the received symbol components is alsocomposed of a repeated sequence of the first block component r_(k) ¹ forup-link transmission as well as the down-link synchronous transmission(τ_(a)=0), as long as Eq. (16) is consistent. Multiplexed receivedcore-symbol r* as well as user specific received core-symbol r*_(k)corresponding to the k-th user have also been composed of such sequencesas to be made by repeating identical blocks r¹ and r_(k) ¹ with periodT_(B) N times, respectively, because the guard sequences are appended.Therefore, the receiver extracts core-symbol part r*, as explained inFIG. 2, then demodulates this extracted core-symbol with a local (thek-th) carrier wave f_(k), and applying an averaging processing to theresultant demodulated symbol to produce a de-spread data-block γ_(k).

FIG. 4 shows spectral components of the transmit-symbols illustrated inFIGS. 2 and 3. F(d_(k)) in FIG. 4( a) is a both sided spectralcharacteristics obtained by analyzing data-block d_(k) in FIG. 2 withDFT (Discrete Fourier Transform) method. It has line spectra atfrequency slots of the integer times as many as frequency f_(B)(=T_(B)⁻¹). If the role-off factor of above-mentioned chip waveform q isassumed to be α(∈ 0˜1), the characteristic has plural line spectra overthe frequency range from 0 to ±{M(1+α)/2}f_(B) in a spacing of f_(B),corresponding to M bits. In a practical equipment, factor a≠0 is used inorder to suppress the oscillation of this chip waveform. This figureshows an example such that the spectra exist for a range from 0 to±Mf_(B), corresponding to a case in which α=1 is assumed. (Though theactual amplitude at ±Mf_(B) is 0, it is shown in the figure by a lowamplitude.)

F(Σ_(k)) is spectra of a core-symbol Σ_(k) (BSS) which is made byrepeating d_(k) N=4 times, and N−1=3 pieces of empty slots between theadjacent spectra are produced as a result of the waveform repetition.F(Σ₁) (solid lines) in FIG. 4( b) shows spectral characteristic of amodulated output s₁ which is produced by modulating a carrier wave f₁illustrated by a data-block sequence Σ₁. The spectra of the dotted linesare equivalent to outputs which are made by modulating carrier wavef₂˜f₄ by Σ₂˜Σ₄, respectively, by the same method as described above, andany frequency slots such as to overlap one another do not exist, becausef_(k) is given by Eq. (8). Therefore, these 4 modulated waveforms aremutually orthogonal.

Above-mentioned received core-symbol component r*_(k) [refer to FIG. 2(c)] is made by repeating N times an identical block component on periodT_(B), similarly to Σ_(k). Therefore, frequency slots which spectrum F(r*_(k)) occupies become identical to that of F(Σ_(k)), and therespective core-symbol components, having different user's ordinalnumbers one another, are orthogonal.

Therefore, by demodulating symbol r* by f_(k) and f_(k′), respectively,demodulated signals γ_(k) ⁰ and γ_(k′) ⁰, corresponding to componentsr*_(k) and r*_(k′)(k′≠k) included in r*, at respective output terminalscan be produced as explained in Eqs. (12) and (13). Thus de-spreaddata-blocks γ_(k) and γ_(k′) can be obtained using these demodulatedsignals, respectively. Thus, the user signal separation can be achieved.

FIG. 5 is a block diagram of a base station transmitter of the firstembodiment example of this invention, and it is composed of atransmit-signal generation block M_(k) ^(D) which has a function ofmaking a signal to be sent to the k-th user (u_(k)), and a common pilotgeneration block M^(P). M bit binary data {b_(k)}/u_(k) and user commonpilot information p=1 are applied to the transmitter as inputs in timedivision manner.

The former is converted into a binary data-block d_(k) consisting of Mchips in Eq. (2) at a data-block generation circuit DBF shown in thefigure. This data-block d_(k) is applied to a repeating circuit REPillustrated which produces a data-block repeated sequence (core-symbol)Σ_(k) with L=NM chips in length by repeating N times as many asdata-block d_(k). In addition, a Guard Inserter circuit GI illustratedproduces a guard added data-block repeated sequence (guard added symbol)Σ_(k) ^(g) with a total sequence length of L_(P)(=NM+L_(g)) by appendinga guard sequence g_(k) which is made by copying the rear L_(g) chips ofΣ_(k), to the front side of Σ_(k).

By applying this chip impulse train to a convoluting multiplier COV, aconvolution product {tilde over (Σ)}_(k) ^(g) convoluted by a chipwaveform q is produced. That is to say, multiplier COV converts discretesignal Σ_(k) ^(g) into a base-band transmit-symbol {tilde over (Σ)}_(k)^(g) of a continuous time waveform over a guard added block spreadsymbol period T_(P)=L_(P)T_(c) (T_(c): chip period).

This base-band-symbol {tilde over (Σ)}_(k) ^(g) is applied to amultiplier MOD₃, where a transmit-symbol s_(k) (BSS) addressed to u_(k)is produced by modulating above-mentioned carrier wave f_(k) allocatedto u_(k) with {tilde over (Σ)}_(k) ^(g). This signal is concurrentlysummed with (K−1) pieces of symbols, made by the same method asdescribed above, addressed to the other users u_(k′)(k′=1,2, . . .K,k′≠k) at an adder Σ, to produce a transmit-symbol (BSS) used for thedown link as shown by the following equation.

$\begin{matrix}{s_{D} = {\sum\limits_{k = 1}^{K}\; s_{k}}} & (17)\end{matrix}$

(For the up-link transmission, above-mentioned symbol s_(k) istransmitted as it is, as a transmit-symbol.)

On the other hand, modulator MOD₁ produces a user common pilot sequencev_(C) with a length of M chips for a timing slot of pilot-information p,different from the timing slot of data inputs. [By appending anupper-script p to a data symbol in FIG. 2, a pilot symbol is expressed.By replacing d_(k) in FIG. 2 for v_(C), a pilot symbol is produced.]

A repeating circuit REP and a guard sequence inserting circuit GI placedbehind MOD₁ append a guard sequence g_(p) by the same method aspreviously described to produce a guard added pilot repeated sequencegiven by the following equation.

Σ_(C) ^(Pg)=T_(CP)[w

v_(C)]  (18)

Convoluting multiplier COV and modulator MOD₂ illustrated produce abase-band pilot symbol {tilde over (Σ)}_(C) ^(Pg) (guard added pilotsymbol), and then modulates common carrier wave f_(C) [for data andpilot time division transmission, f_(k) with an arbitrary subscript kgiven by Eq. (8) can be used as frequency f_(C)] with the guard addedpilot symbol, thereby producing a transmit-pilot symbol s_(p).

A radio-band transmit-symbol s_(f) is obtained, by synthesizing theseoutputs s_(D) and s_(P) at a switch SW, by a method such as to switchthem in time division manner.

A similar block diagram to that in FIG. 5 is used as the composition ofeach user's transmitter for up-link transmission, on condition thatrespective signals v_(C), Σ_(C) ^(pg) and {tilde over (Σ)}_(C) ^(pg) incommon pilot generation block M^(p) in FIG. 5 are replaced by user u_(k)specific signals v_(k) (An user common sequence v_(k)=v_(C) may be alsoused, because user signal separation can be performed with f_(k)), Σ_(k)^(pg) and {tilde over (Σ)}_(k) ^(pg); carrier wave f_(C) is replaced byf_(k), pilot signal s_(p) is replaced by s_(k) ^(p); in addition, addercircuit Σ which synthesizes the other user transmit-symbols s_(k′) isremoved, and symbol s_(f) made by multiplexing s_(k) and s_(k) ^(P) intime division manner at switch SW is transmitted to the base station(BS).

FIG. 6 is a block diagram of a user receiver of the first embodimentexample of this invention, and the receiver is composed of a demodulatedsignal generation block D_(k) ^(D) which demodulates a signal addressedto the k-th user u_(k), a pilot response generation block D_(k) ^(P),and an analyzing circuit AYZ_(k). Block D_(k) ^(P) is also called achannel response generation block between BS and u_(k), having afunction of extracting a pilot symbol which is included in a multiplexedreceived symbol r_(f) received in time division manner corresponding totransmit-symbol s_(f) in FIG. 5 (with an omitted circuit in theillustration).

This extracted output over the pilot period is converted into abase-band-signal γ_(k) ^(p˜) at a modulator MOD₁ and a low pass filterLPF, illustrated to which a local carrier wave of frequency f_(C) hasbeen applied. [In this process, a complex output consisting of real part(I) and imaginary part (Q) components is actually obtained by applyingthe real part cos 2πf_(C)t and the imaginary part sin 2πf_(C)t of thecarrier wave to respective modulators MOD₁ and MOD_(Q), and thenapplying the resultantly obtained outputs to respective low passfilters. Such a detailed circuits used for separating and generating theIQ outputs have been omitted, for simplicity. And, the attenuated powerlevel of received signals is compensated by an equalizing circuit, notshown here.]

On the other hand, a demodulated signal generation block D_(k) ^(D)extracts a data-block spread symbol included in a multiplexed receivedsymbol r_(f) at the data period as well as a pilot in time divisionmanner. To the output, it applies o multiplication processing with alocal carrier wave f_(k), filtering, and averaging, thereby producing ade-spread data-block γ_(k) which consists of M chips, corresponding to Mbit components of data-block d_(k) for the k-th user.

Though signals γ_(k) ^(p˜) and γ_(k) ^(˜) are both continuous timewaveforms, chip waveform correlation circuit C_(or)(q) illustratedproduce correlated outputs between each of these continuous waveformsand a chip waveform q in chip period spacing T_(C). Thus these waveformsare converted into discrete time waveforms, each having a value atdiscrete time spacing. [Useful signal components are included in thesediscrete signals.] That is to say, chip period spacing discretesequences γ_(k) ^(p) and γ_(k) ⁰ are obtained.

On the other hand, a synchronizing circuit SYN produces timing pulsese_(P) and e_(S) illustrated which are synchronized to a principal wave(h_(k0)) of received waves addressed to u_(k), using a framesynchronization signal as described later, and these pulses designatethe time position of synchronized received core-symbol period T_(S). Twogates A extract core-symbols γ*_(k) ^(P) and γ*_(k) ⁰ with respectiveinputs which is denoted by e_(p) and e_(S) illustrated, are by removingthe guard parts from extracted demodulated pilot response γ_(k) ^(P) anddemodulated data symbol γ_(k) ⁰, respectively.

These core-symbols are pilot and data-block repeated sequencesrespectively, and they consist of L(=MN) pieces of chip impulses. Theserepeated sequences are applied to averaging circuits AO₁ illustrated. Byaveraging processing in an unit time of block period T_(B), AO₁ convertsthe sequence length of these signals from MN to M chips, respectively,to output a pilot response p_(k) between BS and u_(k) and de-spreaddata-block γ_(k) addressed to the k-th user. The other user's signalcomponents are removed through this process. Pilot response p_(k) thusproduced is given by the following equations, with user commontransmit-pilot sequence v_(C) and channel characteristic in Eq. (10).

p _(k) =h _(k)

v _(C) +x   (19)

Let's consider an analyzing sequence a(i) such as to be orthogonal tov_(C) at shift positions except for the 0-shift and to satisfy thefollowing equations,

$\begin{matrix}\left. \begin{matrix}{{\frac{1}{M}{\sum\limits_{i = 1}^{M}\; {{v_{C}(i)}{a\left( {i - j} \right)}}}} = 1} & \left( {j = 0} \right) \\{= 0} & \left( {j \neq 0} \right)\end{matrix} \right\} & (20)\end{matrix}$

where i is a chip position variable, a(i−j) is a cyclic j shift periodicsequence of a(i), that is denoted by a_(j) in the figure. If pilotresponse p_(k) is applied to a matched filter MF matched to thecyclically j shift-sequence a(i−j), the following cross correlationfunction with complex amplitude is produced

$\begin{matrix}{{h_{kj}^{0} = {\frac{1}{M}{\sum\limits_{i = 1}^{M}\; {{p_{k}(i)}{a\left( {i - j} \right)}}}}}\left( {{j = {0,1,2,\mspace{11mu} \ldots}}\mspace{14mu},{J - 1}} \right)} & (21)\end{matrix}$

as a response of the transmission channel between base station BS anduser u_(k). Generally, in order to decrease an AWGN component includedin this output h_(kj) ⁰, plural outputs similarly obtained in anadjacent time zone are applied to averaging circuit AO₂ illustrated toproduce a pilot response vector h_(k) which consists of J componentsshown in Eq. (10). This response vector is applied to an analyzingcircuit AYZ_(k) and synchronizing circuit SYN.

Each transmitter transmits a frame which consists of a symbol sequenceand a frame synchronization signal, prepared in advance, and thereceiver establishes receiving synchronization using this framesynchronization signal by well-known means. The receiver applies theframe synchronization outputs e_(sy) produced in this process tosynchronizing circuit SYN. SYN produces timing pulses e_(p) and e_(S) toindicate positions of the data and pilot core-symbols based on e_(sy)and channel response vector h_(k), and transmits these pulses to gates Aillustrated. With the assistance of these timing pulses, core-symbolsγ*_(k) ^(P) and γ*_(k) ⁰ are produced as mentioned above.

Analyzing circuit AYZ_(k) is of composed of a de-correlating detector(DD) or an minimum mean square error detector (MMSE-D) shown in FIG. 18,and produces a soft output vector (estimates) {tilde over(d)}_(k)=({tilde over (b)}_(k1),{tilde over (b)}_(k2), . . . {tilde over(b)}_(kM)) corresponding to M pieces of the data transmitted by adesired station u_(k), by solving Eq. (14) using de-spread data-blockγ_(k) and channel response matrix H composed of channel response vectorh_(k) as mentioned previously. This output is applied to a hard decisioncircuit DEC which makes respective components of vector {tilde over(d)}_(k) on the hard decisions to produce a detected output vector{circumflex over (d)}_(k)=({circumflex over (b)}_(k1),{circumflex over(b)}_(k2), . . . {circumflex over (b)}_(kM)) of a data-block.

The block diagram of a base station receiver for the up-linktransmission takes a composition using respective elements in FIG. 6.That is to say, K pieces of the same circuit as the k-th user receivercircuit RX(u_(k)) in FIG. 6 are prepared corresponding to the userpopulation. A circuit D_(k) ^(P) to be used here is made by replacingcarrier wave f_(C) for D_(k) ^(P) in FIG. 6 by f_(k), and by replacinganalyzing sequence a by sequence a_(k) which is orthogonal to pilotsequence v_(k). It is possible to obtain a detected vector {circumflexover (d)}_(k) using thus modified circuits D_(k) ^(P), D_(k) ^(D), andAYZ_(k) prepared for each user.

A-2. The Multi-Rate Transmission System.

Associated with an increase in data rate to be provided by mobilecommunications systems, respective users desire for use of various kindsof transmission data rates. In this case, it is necessary to avoid thewaste of the frequency resources such as to transmit a low-speed datausing a high-speed transmission channel.

FIG. 7 shows symbol compositions and frequency spectrum characteristicsof multi-rate transmit-symbols as the second embodiment example of thisinvention. Figure (a) shows base-band transmit-symbols Σ_(k) ^(g) (guardadded data-block repeated sequences) which are transmitted by 4 usersu_(k)(k=1,2,3 and 4). (refer to FIG. 2)

In this example, Σ₁ ^(g) and Σ₂ ^(g) are sequences such that data-blocksd₁ and d₂, each having 8 chips corresponding to binary data-block of M=8bits on the block period T_(B) ¹, are arranged repeatedly, and s₃ and s₄are sequences such that data-blocks d₃ and d₄ each having 4 chipscorresponding to M=4 bits on a block period T_(B) ², are arrangedrepeatedly. There is a relation of T_(S)=4T_(B) ¹=8T_(B) ² as shown inthe figure, and the spreading factors of transmit-symbols (s₁,s₂) and(s₃,s₄) are N=4 and 8 respectively. Figure (b) illustrates both sidedspectrum F_(k) ⁰, that is obtained by the same method as that shown inthe lower part of FIG. 4( a). Namely, they are obtained by applying DFTanalysis to Σ_(k) on period T_(S), a part of guard added data-blockrepeated sequence Σ_(k) ^(g). The number of frequency slots in F₃ ⁰ orF₄ ⁰ except f=0 is 8, which is equivalent to a half value in comparisonwith 16, the number of slots for F₁ ⁰ or F₂ ⁰. [similarly to the case inFIG. 4, α=1 is here assumed, and note that actual amplitude at the mostoutside frequency slots takes a value 0.] Spectrum F_(k) illustrated isobtained by modulating orthogonal carrier waves f_(k)(k=1,2,3,4)illustrated by core-symbol Σ_(k), because the spectrum of the modulatedoutputs shifts to the right by f_(k), as shown in Fig. (c). F₁ and F₂are indicated by thick continuous and dotted lines, respectively, in theupper stage of Fig. (c), while (F₃), and (F₄) are shown by thin dottedlines. In the lower part of Fig. (c), F₃ and F₄ are illustrated by thickcontinuous line and dotted lines, respectively.

Frequency spectra made by summing F₃ and F₄ shown in the lower stage iscorrespondent with (F₃) and (F₄) in the upper stage. That is to say, F₃and F₄ alternately utilize the frequency slots whose number is equal tothat used by F₁ or F₂. Therefore, u₃(u₄) transmits symbols with a halftransmission rate as much as that of u₁(u₂), and the channel of u₃(u₄)occupies a half as many as the frequency slots which the channel ofu₁(u₂) occupies corresponding to the full transmission rate.

Channels with different transmission rates can be multiplexed while theorthogonal characteristic between these signals are retained, byproducing thus the transmit-symbols of which spectra are orthogonal eachother. (This orthogonal characteristic holds good for the relationbetween correspondingly received core-symbols.)

As an example, if all users desire for an M=8 bit transmission perdata-block, the service can be provided to K=4 users, if they desire foran M=4 bit transmission, it is given to the K=8 users. Accommodated userpopulation is given by the following equation in a case where all theusers transmit M bits per symbol by assuming that the basic spreadingfactor is N, and the highest data rate is M.

$\begin{matrix}{K = \frac{\overset{\_}{N}\mspace{11mu} \overset{\_}{M}}{M}} & (22)\end{matrix}$

Various transmission rate combined transmission is achieved by dividingand utilizing the basic channel (2M+1 pieces of the frequency slotswhich each basic user occupies) by multiple users, as explained in Fig.(c).

Hence, with the simple method of assigning a frequency slot setconsisting of several pieces of idle frequency slots according to eachuser's request on data rate, highly efficient multi-rate service whichoccupies a band-width in proportion to transmission rate can beachieved. And, the perfect user signal separation can be achieved incases such that whatever the transmission rates are transmitted, becauseeach core-symbol is carried on a common core-symbol period T_(S). Inaddition, the receiver can separate these data symbols by allocating twocarrier waves shown in Eq. (8) to this user, in a case where one usertransmits simultaneously data with two kinds of transmission rates.[Transmit-power each user transmitter needs to transmit one of datasymbol is proportional to the transmission rate. It is because effectivespreading factor N_(e) is inverse proportion to the transmission rate.However, it does not have any harmful effect on the system operation, asthis fact is rational, and the peak transmit-power is constant.]

In the first and the second embodiment examples, the system hasallocated carrier frequency f_(k) to the k-th user, in accurateexpression, a set of frequency slots to be occupied, to each user.Therefore, the spectral efficiency η (bits/band-width) of the system, isgiven by the following equations, where a band-width W is given, andNyquist role-off characteristic denoted by α=0 is assumed.

$\begin{matrix}{\eta = {\frac{KM}{W} = {\frac{KM}{{MN} + L_{g}} \cong 1}}} & (23)\end{matrix}$

And, the approximate value on the right-hand side is obtained, on acondition satisfying K=N and MN>>L_(g).

A-3. Multi-Output User Group Transmission System.

FIG. 8 is the third embodiment example of this invention, indicating atransmitter to receiver diagram and the block diagram of amultiple-output user group transmission system using an identicalcarrier wave. Communications systems using multiple transmit-antennasand multiple receive-antennas are called MIMO (multiple input andmultiple output) systems, and let us here describe a multiple outputsystem equipped with multiple (E pieces) receive-antennas.

FIG. 8( a) shows a user group U_(k′)(k′=1,2, . . . K′) in the down-linktransmission. A common group carrier wave f_(k′) (a common frequencyslot set) is given to the Q users u_(q) ^(fk′)(q=1,2, . . . Q) belongingto group U_(k′). FIG. 8( b) shows transmitter blocks [TX(u₁ ^(f1)) andTX(u₂ ^(f1))] of a base station transmitter TX(BS) which transmitssignals to users belonging to the first user group U₁, and receiverinput blocks [RX(u₁ ^(f1)) and RX(u₂ ^(f1))] of the users (u₁ ^(f1) andu₂ ^(f1)). Two transmit-symbols (s₁ ^(f1) and s₂ ^(f1)) are coherentlysummed by an adder Σ, and the output is transmitted through atransmit-antenna A^(T). (Generally the error rate characteristic can beimproved due to the transmission diversity effect, if each usertransmits with multiple transmit-antennas. It is assumed here to use onetransmit-antenna per user, for simplicity.)

And each receiver demodulates received symbols which have been receivedvia two pairs of receive-antennas (A₁₁ ^(R),A₁₂ ^(R);A₂₁ ^(R),A₂₂ ^(R))at the input side, with group carrier wave f₁ (a case of E=2 is heretaken for an example), and produces de-spread data-blocks (γ₁₁ ^(f1),γ₁₂^(f1);γ₂₁ ^(f1),γ₂₁ ^(f1)). D₁₁ ^(D)˜D₂₂ ^(D) are the same demodulatedsignal generation blocks as D_(k) ^(D) in FIG. 6, and DEM is equivalentto a circuit consisting of LPF, Cor(q), and AO₁ as shown in FIG. 6.Channel characteristics h₁ ^(B1)˜h₂ ^(B2) between transmit-antenna A^(T)and respective of 4 receive-antennas A₁₁ ^(R)˜A₂₂ ^(R) are beforehandgiven to each receiver using the previously mentioned pilot responses.

In a process of generating γ₁₁ ^(f1) and γ₁₂ ^(f1), components whichusers belonging to the other user groups U_(k′) have transmitted areremoved, because group carrier waves f₁ and f_(k′)(k′≠1) applied to bothD₁₁ ^(D) and D₁₂ ^(D), are orthogonal each other. However, a componentcorresponding to signal s₂ ^(f1) which has been transmitted to user u₂^(f1) belonging to the same user group U₁ must be removed, because it isincluded in de-spread data-blocks γ₁₁ ^(f1) and γ₁₂ ^(f1) as aninterfering component. Define a concatenated de-spread data-vector madeby concatenating M-chip vectors γ₁₁ ^(f1) and γ₁₂ ^(f1) in cascade, anda concatenated transmit-data vector which is an element of the abovevector, using transverse superscript ^(T) by the following equations.

$\begin{matrix}\left. \begin{matrix}{\gamma_{1}^{f\; 1C} = \left( {\gamma_{11}^{f\; 1T},\gamma_{12}^{f\; 1T}} \right)^{T}} \\{d^{f\; 1C} = \left( {d_{1}^{f\; 1T},d_{2}^{f\; 1T}} \right)^{T}}\end{matrix} \right\} & (24)\end{matrix}$

Each of these vectors is of 2M chips.

The channel characteristics from the q-th user to the e-threceive-antenna is denoted by h_(q) ^(Be)=(h_(q0) ^(Be),h_(q1) ^(Be), .. . , h_(qJ−1) ^(Be))^(T). A following system of de-correlatingequations holds good,

γ₁ ^(f1C)=Hd^(f1C)+x  (25)

where the parameters range (q ∈ 1,2; e ∈ 1,2).

A partial matrix ĥ_(q) ^(Be) in Eq. (26) takes the same form as that inEq. (14), and it is produced on the basis of channel characteristic(h_(q0) ^(Be),h_(q1) ^(Be), . . . h_(qJ−1) ^(Be)) from base station (BS)to the q-th user u_(q) ^(f1) belonging to user group U₁. H is anextended channel matrix produced of ĥ_(q) ^(Be). An unknown vector{tilde over (d)}^(f1C) made by solving this system by the principle of ade-correlating detector or an MMSE detector is called a soft-outputvector. By making hard decisions on the respective components of thisvector, it is possible to detect respective data. Although a method fordown link transmission is here described, a similar method can beapplied for up-link transmission. That is to say, the number of users tobe accommodated in the system can increase by providing the base stationwith E pieces of receive-antennas.

The efficiency η in Eq. (23) can generally increase by E times, becauseit is possible to set the number of users of each group with E, and thenumber of all the users with K=EN, by using the technology of thisembodiment example.

As the matrix size of the above equations increases with E, theregularity of the matrix degrades, and consequently the error ratecharacteristics degrade. To avoid this problem, by choosing a value lessthan the threshold value for the number of users of each group, forexample, that is E/2, it is possible to increase the number of users ata low error rate.

In the explanation stated above, the user separation techniques forintra-cell users are described. Now, let's describe methods how to avoidthe disturbance due to inter-cell interfering waves as shown in FIG. 1(c).

A-4. Inter-Cell Interference Avoiding System.

FIG. 9 shows a composing method of transmit-symbols such as to avoidinter-cell interference as the fourth embodiment example of thisinvention. FIG. 9 is a time chart showing a symbol composition to beused by the transmitters of a cell correspondent block spreading periodassignment system. θ denotes a symbol showing the cell ordinal number.Ceθ(θ=1,2,3) shows block spread symbols such as shown in FIGS. 2( b) and3(a) which respective transmitters (of base stations or users) locatedin respective of 3 cells produce.

Respective symbols are produced with cell specific parameters [a blockspread symbol period T_(S) ^(θ), a data-block size M^(θ), a spreadingfactor N^(θ) and a carrier frequency f_(k) ^(θ)]. Let a chip ratef_(Ch)=T_(C) ⁻¹ and a guard added block spread symbol period T_(P) becell common values. In this case, the following relation hold goodgenerally for the above parameters (refer to Eqs. (8) and (9)).

$\begin{matrix}\left. \begin{matrix}{T_{P} = {T_{S}^{\theta} + T_{g}^{\theta}}} \\{T_{S}^{\theta} = {M^{\theta}N^{\theta}T_{C}}} \\{f_{S}^{\theta} = \left( T_{S}^{\theta} \right)^{- 1}} \\{f_{k}^{\theta} = {f_{0} + {kf}_{S}^{\theta}}}\end{matrix} \right\} & (27)\end{matrix}$

A parameter set given to respective cells in the example of FIG. 9 is asfollows,

Ce1: M¹=48, N¹=50, T_(S) ¹=2400T_(C) T_(g) ¹=48T_(C)

Ce2: M²=49, N²=49, T_(S) ²=2401T_(C) T_(g) ²=47T_(C)

Ce3: M³=47, N³=51, T_(S) ³=2397T_(C) T_(g) ³=51T_(C)

where a relation T_(P)=2448T_(C) exists.

Now, let's assume a case in which respective base stations in 3 cells Ceθ(θ=1,2,3) have transmitted only transmit-symbols (s_(k) ¹, s_(k) ² ands_(k) ³) using an identical carrier frequency f_(k) addressed to usersbelonging to these respective cells. Let's assume a bad interferencecondition in which a receiver RX (u_(k) ¹) of u_(k) ¹ receives thesesignals under a synchronous condition. Among the signal componentsreceived by u_(k) ¹ in this case, a symbol component addressed to u_(k)¹ is a desired one. The components of a symbol which RX (u_(k) ¹)receives is given by the following equation, if channels h_(k0) ^(Bθ1)are assumed to have only direct waves, corresponding to respectivetransmission paths, for simplicity.

r(u _(k) ¹)=h _(k0) ^(B11) s _(k) ¹ +h _(k0) ^(B21) s _(k) ² +h _(k0)^(B31) s _(k) ³ +x   (28)

When the front part circuit of D_(k) ^(D) shown in FIG. 6 demodulatesthis received signal by common carrier wave f_(k), the demodulatedcore-symbol obtained before the averaging processing contains atransmit-data-block repeated sequence Σ_(k) ^(θ) such as shown in FIG.2( b) as a constituent. Let guard added transmit-symbol period T_(P) beidentical, regardless of the cells, and assuming the synchronousreception, then the demodulated core-symbol (BSS) is given by thefollowing equations

$\begin{matrix}{{\gamma_{k}^{*0}\left( u_{k}^{1} \right)} = {\sum\limits_{\theta = 1}^{3}\; {h_{k\; 0}^{B\; \theta \; 1}{\sum\limits_{k}^{\theta}{+ x}}}}} & (29)\end{matrix}$

In the example in FIG. 9, a core-symbol (block repeated sequence) periodT_(S) ^(θ) is set to be a cell specific value. Consider two cases, oneis to use the same parameter-set (M,N), and the other does a cellspecific one (M^(θ),N^(θ)). When applying the averaging processing tothe above-mentioned outputs, de-spread data-blocks are given by thefollowing equations, respectively,

$\begin{matrix}{{\gamma_{k}^{\theta}\left( u_{k}^{1} \right)} = {{\sum\limits_{\theta = 1}^{3}\; {h_{k\; 0}^{B\; \theta \; 1}d_{k}^{\theta}}} + {x\mspace{20mu} \left( {M,N} \right)}}} & (30) \\{{\gamma_{k}\left( u_{k}^{1} \right)} = {{h_{k\; 0}^{B\; 11}d_{k}^{1}} + {h_{k\; 0}^{B\; 21}d_{k}^{2a}} + {h_{k\; 0}^{B\; 31}d_{k}^{3a}} + {x\mspace{20mu} \left( {M^{1},N^{1}} \right)}}} & (31)\end{matrix}$

where d_(k) ^(θ) is a data-block output which is obtained by applyingrightly averaging to an N^(θ) times data-block repeated output Σ_(k)^(θ) with averaging parameters used by the transmitter, while d_(k)^(θa) shows an output which is obtained by applying the processing withdifferent parameters from those used by the transmitters. The termsd_(k) ² and d_(k) ³ become large interfering components in the casesusing the identical parameter-set in Eq. (30).

Now, let's consider a case using the different parameter-set given byEq. (31). Pay attention to the first chip position (D₁) on symbolcomponent Σ_(k) ¹, contained in the received symbol, (D₁ means atransmit-chip position denoted by m=1 on the respective data-blocks of atransmit-symbol generated in the first cell Ce1.) Let a chip ordinalnumber m (the chip position on the dotted line drawn to the downwardfrom D₁) of respective blocks of the transmit-symbol generated in Ceθ′be a summing chip number. Then the respective chips on the blocks ofcore-symbol Σ_(k) ^(θ′) (θ′≠1) according to the parameter of cell Ce1are summed with respect to the block ordinal number n of atransmit-symbol generated in cell Ce1, to take respective averages. Theresult at the lower stage of FIG. 9 is thus obtained, when using amethod as shown by SCN(θ′−θ)/D₁. Hence, it is understood that the chipordinal numbers constituting demodulated data-block component d_(k)^(θa) in a case of θ′≠θ are randomized. [The sum takes a large valve incase of using a common parameter, because the chip ordinal numbers of areceived signal coming from another cell which arrives at the sametiming as D₁ take always an identical value.] If a number of amplitudeson the different chip number positions are averaged in the summingoperation of the averaging process performed by circuit AO₁ in FIG. 6,both of the mean value and variation approach to zero by law of greatnumbers, because data sequence takes binary (±1).

Therefore, by setting the parameters so that the summed componentsSCN(θ′−θ)(θ′≠θ) based on d_(k) ^(θa) may take enough random values, andby making N^(θ) sufficiently large, it is possible to reduce theinterference power from another cell by (N^(θ))⁻¹ times less. In thissystem, this interference power further decreases due to a carrierfrequency deviation between carrier wave f_(k′) ^(θ′) of the k′(k′≠k)-thuser belonging to Ceθ′(θ′≠θ) and carrier wave f_(k) ^(θ) used for thedemodulation of a receiver of Ceθ, because it enhances the randomizationof the demodulated chips.

FIG. 10 shows a time chart of compositions of transmit-symbol of a cellcorrespondent chip rate assignment system used for the fifth embodimentexample. This system has a function of avoiding inter-cell interferencesimilarly to that in FIG. 9.

Let θ be a cell specific ordinal number. Transmit-symbols are producedusing the cell proper parameters [a spreading factor N^(θ), a number inchip count/core-symbol (L^(θ)=MN^(θ)), and a chip-rate f_(ch) ^(θ) (orchip-period T_(C) ^(θ))], corresponding to cell Ceθ(θ=1,2,3) with thesame method as that explained with FIG. 9. Parameters such asguard-period T_(g), core-symbol-period T_(S), symbol-period T_(P), andblock-size M take respective cell common values generally, and thefollowing relation holds good among the parameters stated above.

$\begin{matrix}\left. \begin{matrix}{T_{P} = {T_{S} + {Tg}}} \\{T_{S}^{\theta} = {{MN}^{\theta}T_{c}^{\theta}}} \\{f_{ch}^{\theta} = {\left( T_{c}^{\theta} \right)^{- 1} = {{MN}^{\theta}/T_{S}}}}\end{matrix} \right\} & (32)\end{matrix}$

In case of M=50, a parameter set given to each cell in the example inFIG. 10 takes the valves as follows.

Ce1: N¹ = 50 L¹ = 2500 T_(C) ¹ = 2500/T_(S) Ce2: N² = 49 L² = 2450 T_(C)² = 2450/T_(S) Ce3: N³ = 48 L³ = 2400 T_(C) ³ = 2400/T_(S)

In this case as well as described above, as de-spread data-blocks, thesame equations as those in Eqs. (30) and (31) are obtained, when theaveraging processing with parameter-sets (N,f_(ch)) and (N^(θ),f_(ch)^(θ)) are applied, respectively, to the demodulated core-symbol γ*_(k)⁰(u_(k) ¹) (BSS) in Eq. (29), in cases where one is to give the commonparameter-set (N,f_(ch)) to all the cells, and the other is to give thecell specific one (N^(θ),f_(ch) ^(θ)) to each cell.

A result shown at the lower stage in FIG. 10 is obtained, when noticingthe first chip position (D₁) of transmit-data-block repeated sequenceΣ_(k) ¹, and indicating the chip ordinal number SCN(θ′−θ)/D₁ to obtainby the same method as the one described with FIG. 9. Therefore, it canbe understood that the chip ordinal numbers constituting de-spreaddata-block component d_(k) ^(θa) in a case of θ′≠θ are randomized.Consequently, inter-cell interference suppressing effect is obtained,similarly to the system described with FIG. 9.

Interference avoiding effect can be acquired, if two kinds ofabove-mentioned interference avoiding systems are widely applied to notonly block spreading CDMA systems but also conventional CDMA systemswhich transmits 1 bit per symbol. Because the symbols coming from theother cells are all randomized in the de-spreading process, even if eachcell uses an identical spreading sequence-set.

A-5. Pilot Transmission System.

FIG. 11 is the sixth embodiment example of this invention, showing atime chart of a symbol frame composition used for pilot transmission. InFig. (a), F_(k) ^(S)(n_(p)) is a symbol frame composed of one piece ofpilot-symbol s_(k) ^(P) and N_(S) pieces of data-symbols s_(k).s_(k)(n_(S)) (n_(S)=1,2, . . . , N_(S)) is the n_(S)-th guard addeddata-block spread symbol s_(k) (BSS) (period T_(P)) as shown in FIG. 2(b) which user u_(k) transmits. s_(k) ^(P)(n_(P)) (n_(p)=1,2, . . . ,N_(P)) is a pilot symbol to be inserted, in time division manner, in then_(P)-th symbol-frame, and the pilot symbol is composed of N (spreadingfactor) pieces of pilot symbols, the n_(P)-th one is denoted byv_(C)(n_(p)) corresponding to v_(C) shown in FIG. 5. Therefore, N_(P)pieces of the pilot symbols to be sequentially transmitted on the N_(P)pieces of the frames constitute a cyclic set. Denoting the symbol-frameperiod and the pilot-frame period by T_(SF), and T_(PF), respectively,the following relation holds good.

$\begin{matrix}\left. \begin{matrix}{T_{SF} = {\left( {N_{S} + 1} \right)T_{P}}} \\{T_{PF} = {N_{P}T_{SF}}}\end{matrix} \right\} & (33)\end{matrix}$

FIG. 11( b) shows a configuration of the n_(P)-th pilot-symbol s_(k)^(P)(n_(p)) which u_(k) transmits, and it takes a form made by replacingdata-block d_(k) in guard added data-block repeated sequence Σ_(k) ^(g)in FIG. 2( b) by v_(C)(n_(P)). The receiver demodulates a receivedpilot-symbol extracted by the synchronizing circuit using the methodexplained with FIG. 6, to produce a channel response h_(kj)(n_(p)) whichcorresponds to h_(kj) ⁰ in Eq. (21).

When applying frequency analysis to a pilot sequence v_(C) composed ofbinary chips, generally the amplitude spectrum does not always have aflat characteristic. Now, let's prepare a sequence set composed of N_(P)pieces of mutually different pilot sequences as mentioned above, so thatthe mean value of the spectral characteristics obtained for thesesequences may become flat. When averaging estimates h_(kj) (n_(p))obtained by Eq. (21) with respect to N_(P) pieces of pilot-symbols, notonly the white noise power contained in the channel-response decreases,but also non-biased frequency characteristics are obtained as thechannel response. If there is uneven distribution in thecharacteristics, the property of data demodulation and detectiondeteriorates, because the channel characteristic h_(k) which thereceiver uses resultantly contains an error.

B. Zero Correlation Zone Sequence Modulation System B-1. Basic System

As another method of performing the user signal separation for amultiplexed received symbol by a receiver, it is known that conventionalsystem (P-5) uses a method of modulating a shift-orthogonal sequenceC_(k) by transmit-data-block d_(k). It is difficult for this system toincrease the spectral efficiency, because the user population K isforced to design less than a half of the sequence length N of sequenceC_(k) as shown in Eq. (E-6).

Let's here use, a well-known Zero-Correlation-Zone sequence (ZCZ) as aspreading sequence. (Kenji Takatsukasa, Shinya Matsufuji, YoshihiroTanada “On Generating Functions for Binary ZCZ Sets of Length 2^(n)”Proceedings of International Symposium on Information Theory and ItsApplications, pp-203-206, 2002. 10)

Now, let

F(Z)=(Z ₁ ,Z ₂ , . . . , Z _(k) , . . . , Z _(K))

Z _(k)=(z _(k1) ,z _(k2) , . . . , z _(kn) , . . . , z _(kN))

be a ZCZ sequence set with length N and family size K, where Z_(k) isthe k-th member sequence and z_(kn) is the n-th chip amplitude [one ofbinary, quadric-phase, or ternary (0, 1, −1) values etc. can be taken].Generally, let denote a sequence which is made by cyclic shifting Z_(k)to the left by b chips by Z_(k) ^(b), and denote the original sequenceby symbol Z_(k) ⁰ shown on the right-hand side in the above equation,when distinction on the shifting number is necessary.

The periodic auto-correlation and cross-correlation functions of thissequence set are given by the following equations,

$\begin{matrix}\left. \begin{matrix}{{\rho_{kk}(\tau)} = {\frac{1}{N}{\sum\limits_{n = 1}^{N}{z_{kn}z_{k,{n + {\tau \mspace{14mu} {({{mod}\; N})}}}}^{*}}}}} \\{{{\rho_{{kk}^{\prime}}(\tau)} = {\frac{1}{N}{\sum\limits_{n = 1}^{N}{z_{kn}z_{k^{\prime},{n + {\tau \mspace{14mu} {({{mod}\; N})}}}}}}}},\mspace{14mu} \left( {k \neq k^{\prime}} \right)}\end{matrix} \right\} & (34)\end{matrix}$

where τ is an integer showing cyclic shift of the sequence, and * showsof a complex conjugate. The ZCZ sequences have the following correlationcharacteristic and the sequence length vs. family size characteristics,for a zero correlation zone τ_(m).

$\begin{matrix}\left. \begin{matrix}{{\rho_{kk}(\tau)} = 1} & \left( {\tau = 0} \right) \\{= 0} & \left( {{\tau \neq 0},\mspace{14mu} {{\tau } \leq \tau_{m}}} \right) \\{{\rho_{{kk}^{\prime}}(\tau)} = 0} & \left( {{{\tau } \leq \tau_{m}},\mspace{14mu} {k \neq k^{\prime}}} \right)\end{matrix} \right\} & (35) \\{K = {\frac{N}{2\tau_{m}}\mspace{14mu} \left( {\tau_{m} \neq 0} \right)}} & (36)\end{matrix}$

Now, let's consider a case of a binary sequence with τ_(m)=1 and N=8 asan example.

In such a case, ρ_(kk)(0)=1, ρ_(kk)(±1)=0, ρ_(kk′)(0)=ρ_(kk′)(±1)=0,(k≠k′); and K=4 are obtained. An example consisting of two differentsequence sets, F₁, and F₂, is shown in the following.

F₁(00000101, 00110110, 01100011, 01010000)

F₂(00110110, 00000101, 01010000, 01100011)

[a chip value 0 indicates −1 for a binary sequence.]

FIG. 12 is the seventh embodiment example of this invention, indicatinga transmit- and a received symbols each of which composed of data-blocksto be processed by the transceiver. FIG. 12( a) shows a process ofproducing a transmit-symbol s_(k) from data-block d_(k) shown in FIG. 2(a) by the similar method to that shown in FIG. 2( b). The differencewith FIG. 2( b) is that multiplication with sequence Z_(k) andmodulation by an user common carrier-wave f_(C) are performed here.

That is to say, a data-block spreading core-symbol Σ_(k) ^(z) consistingof the N pieces of blocks is produced, by multiplying respective chipelements (z_(kn),n=1,2, . . . , N) of the k-th sequence Z_(k), belongingto a ZCZ sequence-set, by a repeated data-block sequence Σ_(k)(core-symbol) made by sequentially arranging N pieces of data-blocks.(This corresponds to generating of a convolution product of Z_(k) andd_(k).) A guard added data-block spread symbol Σ_(k) ^(g) for the k-thuser is produced by appending a guard sequence g_(k) to thiscore-symbol, by the same method as shown in Eqs. (4) and (5).

s_(k) ⁰=Σ_(k) ^(g)=T_(CP)[Z_(k)

d_(k)]  (37)

Each transmitter multiplies symbol Σ_(k) ^(g) by such a chip-wave shownin Eq. (6), to produce a continuous waveform {tilde over (Σ)}_(k) ^(g),and then transmits symbol s_(k) which is produced by modulating a commoncarrier wave f_(C), instead of f_(k) in Eq. (7), with {tilde over(Σ)}_(k) ^(g).

In FIG. 12( b), r is a multiplexed received symbol corresponding to Kpieces of transmit-symbol, and consisting of a sum of user u_(k)correspondent received symbol components r_(k) for K users, as given bythe following equations.

$\begin{matrix}{r = {{\sum\limits_{k = 1}^{K}r_{k}} + x}} & (38)\end{matrix}$

When extracting a core-part r* by removing a guard block r^(g) from thismultiplexed received symbol r, and demodulating the core-part bymultiplying carrier wave f_(C), so as shown in Eq. (12), a base-bandmultiplexed received symbol r*⁰ given by the following equations isproduced,

$\begin{matrix}\left. \begin{matrix}{r^{*0} = {{{\sum\limits_{k = 1}^{K}r_{k}^{*0}} + x} = {{\sum\limits_{n = 1}^{N}{r^{0n}{\delta \left( {l - n} \right)}}} + x}}} \\{r_{k}^{*0} = {\sum\limits_{n = 1}^{N}{r_{k}^{0n}{\delta \left( {l - n} \right)}}}}\end{matrix} \right\} & (39)\end{matrix}$

where r*_(k) ⁰, r_(k) ^(0n), and l are user u_(k) correspondentdemodulated core-symbol, its n-th block component, and a block positionvariable, respectively.

Here, the superscripts ⁰, * and ^(n) indicate a demodulated output bythe local carrier wave, a symbol component made by removing the guardblock, and its n-th block component, respectively. r*⁰ and r*_(k) ⁰ arerespectively composed of r^(0n) and r_(k) ^(0n)(n=1,2, . . . , N), asshown in FIG. 12. r*_(k) ⁰ is composed of multi-path-components of 3waves, as shown in FIG. 12( b), when the channel characteristic of J=3is assumed in Eq. (10). Blank block parts illustrated show receivedcomponents (H_(k0)Σ_(k) ^(z)) of the present (concurrent) symbol-blocks,while hatched block parts show received components (H_(k1)Σ_(k) ^(z)) ofdelayed waves from the preceding symbol-blocks to the present blocks.H_(k0) and H_(k1) are the principal wave and the delayed wave channelmatrices.

Considering arriving time difference τ_(a) (refer to FIG. 3) of receivedsymbol component r_(k), when setting received symbol component r₁ as areference time, the channel matrices stated above can be generalizedinto H_(k0)(a) and H_(k1)(a), with channel characteristic h_(k) and timedifference τ_(a). They take forms corresponding to the upper right andthe lower left triangle matrices in Eq. (14). Examples in case of J=3and a=0, 1 are given by the following equations.

$\begin{matrix}{\left. \begin{matrix}{H_{1}^{0} = \begin{bmatrix}\; & \ddots & h_{2} & h_{1} \\\; & \; & \ddots & h_{2} \\\; & \; & \; & \ddots \\0 & \; & \; & \;\end{bmatrix}} \\{H_{0}^{0} = \begin{bmatrix}h_{0} & \ddots & \; & \; & 0 \\{\; h_{1}} & h_{0} & \ddots & \; & \; \\h_{2} & h_{1} & \; & \ddots & \; \\\; & h_{2} & \ddots & h_{0} & \ddots \\\; & 0 & \; & h_{1} & h_{0}\end{bmatrix}}\end{matrix} \right\} \mspace{14mu} \left( {{J = 3},\mspace{14mu} {a = 0}} \right)} & (40) \\{\left. \begin{matrix}{H_{1}^{1} = \begin{bmatrix}\ddots & h_{2} & h_{1} & h_{0} \\\; & \ddots & h_{2} & h_{1} \\\; & \; & \ddots & h_{2} \\0 & \; & \; & \ddots\end{bmatrix}} \\{H_{0}^{1} = \begin{bmatrix}\ddots & 0 & \; & \; & \; & \; \\h_{0} & \ddots & \; & \; & \; & \; \\h_{1} & h_{0} & \ddots & \; & \; & \; \\h_{2} & h_{1} & \ddots & \ddots & \; & \; \\\ddots & h_{2} & \; & h_{0} & \ddots & 0 \\\; & \ddots & \; & h_{1} & h_{0} & \ddots\end{bmatrix}}\end{matrix} \right\} \mspace{14mu} \left( {{J = 3},\mspace{14mu} {a = 1}} \right)} & (41)\end{matrix}$

The n-th block component of the multiplexed demodulated core-symbol inEq. (39) consists of above-mentioned preceding block component andpresent block component, as given by the following equations. (hereaftera=0 is assumed for simplicity, and the indication of “a” is omitted)

$\begin{matrix}\left. \begin{matrix}{r_{k}^{0n} = {r_{k\; 1}^{0n} + r_{k\; 0}^{0n}}} \\{r_{k\; 1}^{0n} = {H_{k\; 1}\left( {z_{k,{n - 1}}d_{k}} \right)}} \\{r_{k\; 0}^{0n} = {H_{k\; 0}\left( {z_{k,n}d_{k}} \right)}}\end{matrix} \right\} & (42)\end{matrix}$

Here, H_(k0) and H_(k1) made by appending a subscript k to the symbolsin Eqs. (40) and (41) are used, because a channel characteristic fromu_(k) (or to u_(k)) must be used. Symbol component r_(k1) ^(0n) showsthe hatched part, and r_(k0) ^(0n) dose the blank part at the loweststage in FIG. 12( b).

De-spread outputs are obtained here by multiplying the multiplexeddemodulated core-symbol r*⁰ by sequence Z_(k)=Z_(k) ⁰ allocated todesired user u_(k), and sequence Z_(k) ⁻¹ made by cyclic shifting Z_(k)⁰ by 1 chip right-ward, respectively. A de-spread data-block given bythe following equation is obtained, by averaging these outputs in anunit of period T_(B),

$\begin{matrix}\left. \begin{matrix}{\gamma_{k} = {\frac{1}{N}\left\{ {\sum\limits_{n = 1}^{N}\left( {{r^{0n}z_{{kn} - 1}^{*}} + {r^{0n}z_{kn}^{*}}} \right)} \right\}}} \\{= {{H_{k\; 1}d_{k}} + {H_{k\; 0}d_{k}} + x}} \\{= {{H_{k}d_{k}} + x}}\end{matrix} \right\} & (43)\end{matrix}$

where a relation H_(k)=H_(k1)+H_(k0) is used. De-spread data-blocksγ_(k/−1) ⁰ and γ_(k/0) ⁰ in FIG. 12( c) are averaged componentscorresponding to r^(0n)z_(kn−1) and r^(0n)z_(kn) in the above equation.

In order to correlatively separate present block components and thepreceding block components of the k-th user from another user'scomponents using spreading sequence Z_(k) and the 1 chip right shiftedsequence Z_(k−1), the following relation is required, for zerocorrelation zone τ_(m) (an integer normalized by T_(C)) and the largestdelay time (τ_(aM)+τ_(DM)) in Eq. (16).

$\begin{matrix}\left. \begin{matrix}{{\tau_{aM} + \tau_{DM}} \leq {\tau_{m}T_{B}}} \\{T_{B} = {MT}_{C}}\end{matrix} \right\} & (44)\end{matrix}$

In this case, it is generally possible to hold τ_(m)=1 for a high speeddata-rate transmission, by choosing M to be a large value.

The above equations show that a received symbol component addressed touser u_(k) corresponding to the transmit-data-block can be separatelyextracted from multiplexed received symbol r, based on the orthogonalityin Eq. (35). When applying well-known means such as a de-correlatingdetector or an minimum mean square error detector to Eq. (43), it ispossible to obtain an estimate vector {tilde over (d)}_(k) oftransmitted data vector d_(k),

$\begin{matrix}\left. \begin{matrix}{{\overset{\sim}{d}}_{k} = {\left\lbrack H_{k} \right\rbrack^{- 1}\gamma_{k}}} & \lbrack{DD}\rbrack \\{{\overset{\sim}{d}}_{k} = {\left\lbrack {{H_{k}^{H}H_{k}} + {N_{r\; 0}I_{M}}} \right\rbrack^{- 1}H_{k}^{H}\gamma_{k}}} & \lbrack{MMSE}\rbrack\end{matrix} \right\} & (45)\end{matrix}$

where H_(k) ^(H), N_(r0) and I_(M) are Hermitian transposed matrix ofH_(k), AWGN power included in de-spread output γ_(k), and an identitymatrix with size M×M. A data-block detected output vector of user u_(k)in Eq. (15) is obtained, when making respective components of vector{tilde over (d)}_(k) on the hard decisions.

FIG. 13 is an eighth embodiment example of this invention, showing ablock diagram of the transceiver for the up-link transmission. Figure(a) shows a transmit-signal generating block M_(k) ^(D) for the datatransmission of user u_(k), while Fig. (b) does a demodulated signalgenerating block D_(k) ^(D) and a detected output generating block of abase-station receiver (illustration of generating and demodulatingblocks of the pilot-symbol is omitted).

Figure (a) is a composition made by replacing sequence repeating circuitREP shown in FIG. 5 by a block spreading circuit BS. Circuit BS outputsa core-symbol Σ_(k) ^(z) by obtaining a convolution product of spreadingsequence Z_(k) and data-block d_(k). Guard insertion circuit GI appendsa guard sequence to core-symbol Σ_(k) ^(z), multiplies a resultantoutput of GI by chip-waveform q at convoluting multiplier COV, andthereby produces a base-band transmit-symbol {tilde over (Σ)}_(k) ^(g)with continuous waveform. Modulator MOD₁ modulates a common carrier wavef_(C) by {tilde over (Σ)}_(k) ^(g) to produce a transmit-symbol s_(k).

FIG. 13( b) shows a composition such as made by additionally inserting amodulator MOD₃ between gate A and averaging circuit AO₁ shown in FIG. 6.Multiplexed received symbol r is converted into a multiplexeddemodulated core-symbol r*⁰ having amplitude values on discrete timingsat the circuits from modulator MOD₂ to gate A. Modulator MOD₃ produces ademodulated core-symbol in FIG. 12 by de-spreading core-symbol r*⁰ withZ_(k) ⁰, and Z_(k) ⁻¹. Circuit AO₁ produces a de-spread data-block γ_(k)by averaging it, as an user signal separated output.

The function of the succeeding circuits in the figure is the same asthat in FIG. 6. Furthermore, a down-link transmission system having thesame operating principle can be constructed by means such that thebase-station and the users have the same transmitting and receivingfunctions as those stated above, respectively.

The method stated above results in a relation of K=N/2 for sequencelength N, reducing a possible user population to be accommodated forspreading factor to a half in comparison with that of system A. Let'sexplain a method to double the user population so as to be K=N.

B-2. Highly Efficient Transmission System.

Let's assign two kinds of shifted ZCZ sequences to 2 users u_(k1) andu_(k2) as the following, respectively.

u _(k) ⁰ :Z _(k) ⁰=(z _(k1) ⁰ ,z _(k2) ⁰ , . . . , z _(kN) ⁰)

u _(k) ¹ :Z _(k) ¹=(z _(k2) ¹ ,z _(k3) ¹ , . . . , z _(kN) ¹ ,z _(k1) ¹)

That is to say, Z_(k) ¹ is a sequence made by cyclic shifting a sequenceZ_(k) ⁰=(Z_(k)) to the left by 1 chip. Therefore, there is a relation ofz_(kn) ¹=z_(kn+1) ⁰ between respective chip amplitudes of thesesequences. A base-band block spreading transmit-symbol similar to Eq.(37) is given by the following equation.

s _(k) ^(0Q) =T _(CP) └Z _(k) ^(Q)

d _(k) ^(Q)┘ (Q ∈ 0,1)   (46)

If such a transmit-symbol made by modulating common carrier-wave f_(C)is sent out from each of the N users designated by parameters (k=1˜N/2,Q=0, 1), the (multiplexed) received symbol is given by

$\begin{matrix}{r = {\sum\limits_{k = 1}^{N/2}{\sum\limits_{Q = 0}^{1}r_{k}^{Q}}}} & (47)\end{matrix}$

A base-band output made by demodulating the received symbol by thecarrier wave is given by the following equations, when using the samesymbols as used in Eqs. (39) and (42) (there is only a differencedenoted by Q),

$\begin{matrix}\left. \begin{matrix}{r^{*0} = {{\sum\limits_{Q = 0}^{1}{\sum\limits_{k = 1}^{N/2}r_{k}^{Q*0}}} = {\sum\limits_{n = 1}^{N}{r^{0n}{\delta \left( {l - n} \right)}}}}} \\{r_{k}^{Q*0} = {\sum\limits_{Q = 0}^{1}{\sum\limits_{n = 1}^{N}{r_{k}^{Q\; 0n}{\delta \left( {l - n} \right)}}}}}\end{matrix} \right\} & (48) \\\left. \begin{matrix}{r_{k}^{Q\; 0n} = {r_{k\; 1}^{Q\; 0n} + r_{k\; 0}^{Q\; 0n}}} \\{r_{k\; 1}^{Q\; 0n} = {H_{k\; 1}\left( {z_{k,{n - 1}}^{Q}d_{k}^{Q}} \right)}} \\{r_{k\; 0}^{Q\; 0n} = {H_{k\; 0}\left( {z_{k,n}^{Q}d_{k}^{Q}} \right)}}\end{matrix} \right\} & (49)\end{matrix}$

Let Z_(k) ⁰(0) be a sequence made by shifting Z_(k) ⁰(−1) to the rightby 1 chip. Then a de-spread vector given by the following equation isobtained, considering a relation of Z_(k) ⁰(0)=Z_(k) ¹(−1), byde-spreading the respective components of r_(k) ^(Q)*⁰ using sequenceZ_(k) ⁰(0).

$\begin{matrix}\left. \begin{matrix}{\gamma_{k} = {\frac{1}{N}\left\{ {\sum\limits_{n = 1}^{N}{r^{0n}z_{kn}^{*}}} \right\}}} \\{= {{H_{k\; 0}d_{k}^{0}} + {H_{k\; 1}d_{k}^{1}} + x}}\end{matrix} \right\} & (50)\end{matrix}$

Now, the following equations are obtained, when solving de-spread vectorγ_(k) to produce data-vector d_(k) ⁰ with an MMSE detector using thesymbols in Eq. (45),

$\begin{matrix}\left. \begin{matrix}\begin{matrix}{\overset{\sim}{d} = {\left\{ {{H_{k\; 0}^{H}H_{k\; 0}} + {N_{r\; 0}I_{M}}} \right\rbrack^{- 1}\left\lbrack {H_{k\; 0}^{H}\gamma_{k}} \right\rbrack}} \\{= {d_{k}^{0} + d_{k}^{0I} + x^{0}}}\end{matrix} \\{d_{k}^{0I} = {\rho_{Z}^{0/1}d_{k}^{1}}} \\{\rho_{Z}^{0/1} = {\left\lbrack {{H_{k\; 0}^{H}H_{k\; 0}} + {N_{r\; 0}I_{M}}} \right\rbrack^{- 1}\left\lbrack {H_{k\; 0}^{H}H_{k\; 1}} \right\rbrack}}\end{matrix} \right\} & (51)\end{matrix}$

where, d_(k) ^(0I) and ρ_(Z) are an interfering component due to d_(k) ¹which is included in γ_(k), and an interfering matrix from d_(k) ¹ tod_(k) ^(0I), respectively. The following equations are obtained, whensolving γ_(k) similarly to produce d_(k) ¹ with an MMSE detector.

$\begin{matrix}\left. \begin{matrix}\begin{matrix}{\overset{\sim}{d} = {\left\{ {{H_{k\; 1}^{H}H_{k\; 1}} + {N_{r\; 0}I_{M}}} \right\rbrack^{- 1}\left\lbrack {H_{k\; 1}^{H}\gamma_{k}} \right\rbrack}} \\{= {d_{k}^{1} + d_{k}^{1I} + x^{1}}}\end{matrix} \\{d_{k}^{1I} = {\rho_{Z}^{1/0}d^{0}}} \\{\rho_{Z}^{1/0} = {\left\lbrack {{H_{k\; 1}^{H}H_{k\; 1}} + {N_{r\; 0}I_{M}}} \right\rbrack^{- 1}\left\lbrack {H_{k\; 1}^{H}H_{k\; 02}} \right\rbrack}}\end{matrix} \right\} & (52)\end{matrix}$

For concatenated vectors of the following equations based on Eqs. (51)and (52),

$\begin{matrix}\left. \begin{matrix}{d_{k}^{C} = \left\lbrack {d_{k}^{0T},d_{k}^{1T}} \right\rbrack^{T}} \\{{\overset{\sim}{d}}_{k}^{C} = \left\lbrack {{\overset{\sim}{d}}_{k}^{0T},{\overset{\sim}{d}}_{k}^{1T}} \right\rbrack^{T}}\end{matrix} \right\} & (53)\end{matrix}$

a system of linear equations represented by the following equations,

is obtained, where H_(C) is a correlation matrix with size 2M×2M. Asoft-output of a concatenated vector d_(k) ^(C) is obtained by thefollowing equation, with such a method as multiplying {tilde over(d)}_(k) ^(C) in Eq. (54) by an inverse matrix of H_(C).

[{tilde over (d)} _(k) ^(C) ]=H _(C) ⁻¹ {tilde over (d)} _(k) ^(C)  (55)

By making it on the hard decisions the respective components ofsoft-output vector with length 2M, a {circumflex over (d)}_(k) ^(C) isobtained. Therefore, it is possible to obtain {circumflex over (d)}_(k)⁰ and {circumflex over (d)}_(k) ¹ of data-blocks which have beentransmitted by two users u_(k) ⁰ and u_(k) ¹ using the k-th ZCZ sequenceZ_(k).

However, it is impossible to obtain all the values {circumflex over(b)}_(km) ¹, those are the components of {circumflex over (d)}_(k) ¹.Received symbol components which correspond to (M−J+1) bits from thehead of data-block d_(k) are not included in the delayed wave componentsappearing on a block shifted to the right side by 1 block. Because thenumber J of the multi-path-waves must be designed in this system so asto satisfy a condition of J≦(M+1) based on the relating equations inEqs. (35) and (44).

That is to say, it is impossible to detect data corresponding to the(M−J+1) bits from the head of d_(k) ¹, when using the above-mentionedmethod, because the second term H_(k1)d_(k) ¹ on the right-hand side ofde-spread vector γ_(k) shown in Eq. (50) does not contain theabove-described components.

Then, let's notice hard decision output {tilde over (d)}_(k) ⁰ of {tildeover (d)}_(k) ⁰ obtained from Eq. (55). By obtaining this solution forall of k, a component corresponding to all the users u_(k) ⁰ using Z_(k)⁰ which is included in multiplexed demodulated core-symbol r⁰ can beestimated, by the following equations as a reproduced symbol component({tilde over (d)}_(k) ⁰ may be used instead of {circumflex over (d)}_(k)⁰, for a high signal to noise ratio).

$\begin{matrix}{w^{0} = {\sum\limits_{k = 1}^{K}\; {H_{k\; 1}\left\lbrack {T_{CP}\left\{ {Z_{k}^{0} \otimes {\hat{d}}_{k}^{0}} \right\}} \right\rbrack}}} & (56)\end{matrix}$

The first part I (component corresponding to Q=1) of the multiplexeddemodulated core-symbol which is made by removing reproduced componentw⁰ from the multiplexed demodulated symbol is obtained by the followingequation.

$\begin{matrix}{r^{1^{*}0} = {{r^{\;^{*}0} - w^{o}} = {\sum\limits_{n = 1}^{N}\; {\gamma^{10n}{\delta \left( {l - n} \right)}}}}} & (57)\end{matrix}$

This symbol includes a little component corresponding to d_(k) ⁰ if itis assumed that the major components of {circumflex over (d)}_(k) ⁰ arecorrect.

Therefore, when de-spreading this symbol by the same means as explainedwith Eq. (43) to produce a sum of the present block components anddelayed block components, a de-spread data-block is obtained by thefollowing equation,

$\begin{matrix}\left. \begin{matrix}{\gamma_{k}^{1} = {\frac{1}{N}\left\{ {{\sum\limits_{n = 1}^{N}{r^{10n}z_{{kn} + 1}^{*}}} + {r^{10n}z_{kn}^{*}}} \right\}}} \\{= {{H_{k\; 1}d_{k}^{1}} + {\Delta \; {d_{k}^{1}\left( w^{0} \right)}} + x}}\end{matrix} \right\} & (58)\end{matrix}$

where Δd_(k) ¹(w⁰) is an error component due to the error of w⁰. Solvingthe data block with an MMSE detector,

{tilde over (d)} _(k) ¹ =[H _(k1) ^(H) H _(k1) +N _(r0) I _(M)]⁻¹ H_(k1) ^(H)γ_(k) ¹   (59)

is obtained. A detected output vector {circumflex over (d)}_(k) ¹similarly to Eq. (15) is obtained, by making it on the hard decisions,the respective components of {tilde over (d)}_(k) ¹.

Now, let's obtain all of vectors {circumflex over (d)}_(k) ¹ for Kusers, and thereby produce reproduced symbol components corresponding toall the users of u_(k) ¹.

$\begin{matrix}{w^{1} = {\sum\limits_{k = 1}^{K}\; {H_{k\; 1}\left\lbrack {T_{CP}\left\{ {Z_{k}^{1} \otimes {\hat{d}}_{k}^{1}} \right\}} \right\rbrack}}} & (60)\end{matrix}$

The 0-th part of the multiplexed demodulated core-symbol (correspondingto Q=0), made by removing the above component from the multiplexeddemodulated symbol is expressed by the following equation.

$\begin{matrix}{r^{0^{*}0} = {{r^{\;^{*}0} - w^{1}} = {\sum\limits_{n = 0}^{N}\; {r^{0n}{\delta \left( {l - n} \right)}}}}} & (61)\end{matrix}$

In r⁰*⁰, most of the components carrying d_(k) ¹ have been removed.

Therefore, when de-spreading the above output, the following de-spreaddata-block

$\begin{matrix}\left. \begin{matrix}{\gamma_{k}^{0} = {\frac{1}{N}\left\{ {{\sum\limits_{n = 1}^{N}{r^{0n}z_{kn}^{*}}} + {r^{0n}z_{{kn} - 1}^{*}}} \right\}}} \\{= {{H_{k\; 1}d_{k}^{0}} + {\Delta \; {d_{k}^{0}\left( w^{1} \right)}} + x}}\end{matrix} \right\} & (62)\end{matrix}$

is obtained. Thus, it is possible to obtain a detected output vector{circumflex over (d)}_(k) ⁰ in the same way as explained with Eq. (59).This output has higher accuracy than that obtained with soft-output{circumflex over (d)}_(k) ^(C) in Eq. (55), because this method canutilize additionally the preceding block components. By repeating theabove-described processing multiple times to produce {tilde over(d)}_(k) ⁰ and {tilde over (d)}_(k) ¹ in turn, the error component whichthe previous soft-output has contained reduces, resulting in productionof detected output {circumflex over (d)}_(k) ⁰ and {circumflex over(d)}_(k) ¹ with less error. These analyzing operations are carried outat AYZ_(k) in FIG. 13( b).

It is possible to increase the total user population to a value k=N.

B-3. Multi-Rate Transmission System.

FIG. 14 is the ninth embodiment example of this invention, showing aconfiguration of the transmit-symbol for multi-rate transmissionsystems. For simplicity, let F(Z^(A)) be the first ZCZ sequence set tobe used for the user signal separation, and let Z_(k) ^(A)(=z_(k1)^(A),z_(k2) ^(A), . . . , z_(kN) ^(A)) be the k-th sequence (it iscalled hereafter sequence A).

By setting the sequence length to be N=N^(A)=4, and assuming τ_(m)=1 inbasic system B-1, it leads to N^(A)/2=2 as the user population K fromEq. (31). Let F(Z^(B)) be the second ZCZ sequence set to be used foruser signal separation and rate setting, and let Z_(k) ^(B)(=z_(k1)^(B),z_(k2) ^(B), . . . , z_(kN) ^(B)) be the k-th member sequence (itis called hereafter sequence B), then it results in N^(B)/2=2 as thefamily size of the sequence-set, for the sequence length of N=N^(B)=4.Under the above-described condition, the number of total users is givenby K_(T)=N^(A)N^(B)/4=4, when allocating respective sequences of asequence-set (Y_(k′)) composed of Z_(k) ^(A) and Z_(k′) ^(B) to theindividual users.

Let's consider a case of 3 users where allocating a spreading sequenceY₁=Z₁ ^(A) to user u₁, and Y₂=(Z₂ ^(A),Z₁ ^(B)) [Y₃=(Z₂ ^(A),Z₂ ^(B))]to u₂(u₃). Y₂(Y₃) is made by means of making a convolution product of Z₁^(B)(Z₂ ^(B)) and Z₂ ^(A), as given by the following equations.

$\begin{matrix}\left. \begin{matrix}{Y_{2} = {Z_{2}^{A} \otimes Z_{1}^{B}}} \\{Y_{3} = {Z_{2}^{A} \otimes Z_{2}^{B}}}\end{matrix} \right\} & (63)\end{matrix}$

A transmit-symbol s_(k) of user u_(k) is produced, by modulating usercommon carrier wave f_(C) by a base-band-symbol s_(k) ⁰ (BSS) which isproduced by replacing Z_(k) by Y_(k) in Eq. (37).

FIG. 14( a) shows a production order such that a base-band core symbols₁ ⁰=(s₁₁ ⁰,s₁₂ ⁰, . . . s_(1N) ⁰) (N=N^(A)) is produced, by spreading adata-block d₁ (data-block period T^(A)) of user u₁ with spreadingsequence Z₁ ^(A)(=Y₁) (corresponding chip wise product as illustrated),and then a transmit-symbol s₁ (BSS) is produced by modulating carrierwave f_(C) by a guard added base-band-symbol made by appending a guardsequence g₁ to the core-symbol.

In Fig. (b), Σ₂ is a repeated sequence of a data-block d₂ (data-blockperiod T^(B)=T^(A)/4) of user u₂. A sequence made by making aconvolution product of sequence Z₁ ^(B) and Z₂ ^(A) illustrated isdenoted by Y₂(=y₂₁,y₂₂, . . . , y_(2N)) (N=N^(A)N^(B)) (that is to makea corresponding chip wise product as illustrated). The figure indicatessuch a process that a base-band-symbol s₂ ⁰[s_(2n) ⁰=y_(2n)d₂] isproduced by making a product of Σ₂ and Y₂, and a transmit-symbol s₂ isproduced by modulating carrier wave f_(C) by this symbol.

The respective components of a multiplexed received symbol r which abase-station BS has received on quasi-synchronous condition, take thesame composition as that in FIG. 3( b), and the symbol consists of 3received symbol components r₁, r₂ and r₃ corresponding totransmit-symbols s₁, s₂ and s₃.

By de-spreading received symbol r with respective multiplications of Z₁^(A)(0) and Z₁ ^(A)(−1) as shown in FIG. 12( c) and Eq. (43), and thenaveraging the de-spread signal in an unit of period T^(A), it ispossible to obtain de-spread data-block γ₁ ^(A) (sequence length M¹)corresponding to a received symbol component r₁ coming from user u₁.And, a de-spread data-block γ₂ ^(A) (sequence length M¹) obtained bysimilarly de-spreading received symbol r by Z₂ ^(A)(0) and Z₂ ^(A)(−1),and then averaging the resultant outputs, corresponds to the sum ofcomponents r₂ and r₃. When de-spreading further the latter γ₂ ^(A) bysequences B [Z₁ ^(B)(0) and Z₁ ^(B)(−1)] and [Z₂ ^(B)(0) and Z₂^(B)(−1)], respectively, and then averaging the de-spread outputs in anunit of period T^(B), de-spread data-blocks γ₂ ^(B) and γ₃ ^(B) (eachhaving a sequence length M²) can be obtained, respectively,corresponding to received symbol components r₂ and r₃ coming from usersu₂ and u₃.

That is to say, by de-spreading and averaging symbol r by 2 pieces ofsequences A, outputs corresponding to component r₁ can be separated fromcomponents (r₂ and r₃), and components r₂ and r₃ can be separated byde-spreading the latter components (r₂ and r₃) and averaging them by twosequences B. When applying the method shown in Eq. (45) to de-spreaddata-blocks γ₁ ^(A), γ₂ ^(B) and γ₃ ^(B) thus obtained, with channelmatrix H_(k) produced from the channel characteristics between u_(k) andBS, inter-bit interference can be removed to obtain a soft-output vector{tilde over (d)}_(k), thus leading to producing a detected output vector{circumflex over (d)}_(k).

The service range of transmission data rate can be widely established bythe above-mentioned multi-rate transmission system, because this systemcan be generalized as a system which is constructed by makingconvolution products of respective sequences which are exclusivelychosen from respective stages of a multi-stage ZCZ sequence set. Thenumber of simultaneous users on service increases, in a case where manyof low rate users take place. And, total transmission data ratedecreases to a half in the every stage, in cases where basic system B-1is used. However, in cases where high-efficient transmission system B-2is applied, the data-rate reduction dose not arise, even if the numberof sequence stages increases, therefore the high spectral efficiency canbe achieved.

B-4. Multi-Output User Group Transmission System.

Let's explain an embodiment example which increases the available userpopulation by a method using multiple of receive-antennas similarly to asystem explained in A-3. Although the example of the two usertransmission system using identical carrier wave is described in A-3,zero correlation zone sequence modulation systems use a common carrierwave. Let's explain here, user signal separation techniques to increasethe user population, under a condition of using one ZCZ sequence Z_(k)and increasing the number of the receive-antennas.

FIG. 15 shows a system diagram from transmitter to receiver as theten-th embodiment example of this invention, and a block diagram of amulti-output user group transmission system using an identical spreadingsequence. Figure (a) is a diagram of an up-link transmission system inwhich Q users belonging to each of user groups U_(k)(k=1,2, . . . , K)transmit their signals with an identical spreading sequence Z_(k).

FIG. 15( b) is a block diagram showing functions such that Q=2 usersbelonging to the first user group U₁ transmit signals from thetransmit-antennas A₁ ^(T) and A₂ ^(T) of their transmitters TX (u₁^(z1)) and TX (u₂ ^(z1)), a base-station receiver RX(BS) equipped with 2receive-antennas A₁ ^(R) and A₂ ^(R) produces de-spread data-blocksγ¹(U₁) and γ²(U₁) illustrated, by separating the respective componentswhich users u₁ ^(z1) and u₂ ^(z1) have transmitted. h_(q) ^(Re) (q: anuser number inside each group, e: receive-antenna number) shows achannel characteristic between the transmit- and receive-antennas. 2pieces of {circumflex over (D)}₁ ^(D) are the same circuits as the frontpart of the data demodulating block in FIG. 13, producing multipledemodulated core-symbols r₁ ^(e)*⁰.

A circuit AO averages a de-spread signal made by multiplying symbol r₁^(e)*⁰ by spreading sequence Z₁ used by the transmitters, to obtain 2pieces of de-spread data-blocks. By concatenating these data-blocks, aconcatenated demodulated vector is produced,

$\begin{matrix}\left. \begin{matrix}{{\gamma^{C}\left( U_{1} \right)} = \left\{ {{\gamma^{1}\left( U_{1} \right)}^{T},{\gamma^{2}\left( U_{1} \right)}^{T}} \right\}^{T}} \\{{\gamma^{1}\left( U_{1} \right)} = {{{\hat{h}}_{1}^{B\; 1}{d_{1}\left( U_{1} \right)}} + {{\hat{h}}_{2}^{B\; 1}{d_{2}\left( U_{1} \right)}} + x_{1}}} \\{{\gamma^{2}\left( U_{1} \right)} = {{{\hat{h}}_{1}^{B\; 2}{d_{1}\left( U_{1} \right)}} + {{\hat{h}}_{2}^{B\; 2}{d_{2}\left( U_{1} \right)}} + x_{2}}}\end{matrix} \right\} & (64)\end{matrix}$

where, ĥ_(q) ^(Be) is a channel matrix taking the same form as thetriangular matrix ĥ_(q) ^(Be) in Eq. (26) which is made by using channelcharacteristic h_(q) ^(Be)=(h_(q0) ^(Be),h_(q1) ^(Be), . . . , h_(qJ−1)^(Be)) between the q-th user of group U₁ and base-station BS.

Hence, based on this relation, the following equation is obtained wheresymbol U₁ is omitted for simplicity,

$\begin{matrix}\left. \begin{matrix}{\gamma^{C} = {{Hd}^{C} + x}} \\{\begin{pmatrix}\gamma^{1} \\\gamma^{2}\end{pmatrix} = {{\begin{pmatrix}{\hat{h}}_{1}^{B\; 1} & {\hat{h}}_{2}^{B\; 1} \\{\hat{h}}_{1}^{B\; 2} & {\hat{h}}_{2}^{B\; 2}\end{pmatrix}\begin{pmatrix}d^{1} \\d^{2}\end{pmatrix}} + \begin{pmatrix}x_{1} \\x_{2}\end{pmatrix}}}\end{matrix} \right\} & (65)\end{matrix}$

where, H is an extended channel matrix. By solving the above equationsfor concatenated data-block d^(C) by the method in Eq. (45), soft-outputvectors {tilde over (d)}₁(U₁) and {tilde over (d)}₂(U₂) can be obtained.Detected output vectors are obtained by making it on the hard decisionsthe respective components of these vectors. Thus, using one ZCZsequence, two user signals can be separated. E times many more usersignals can be generally separated, without increasing the frequencyband occupancy, by using E pieces of receive-antennas.

B-5. Inter-Cell Interference Avoidance System.

For respective of systems B-1 to B-4, the same effect as stated abovecan be obtained by applying inter-cell interference avoiding technologyexplained with system A-4.

In addition, for systems B, can be designed plural sets of zerocorrelation zone sequences with an identical sequence length, such asdifferent sequence sets F₁ and F₂ described with system B-1.Cross-correlation values among the member sequences, each belonging to adifferent sequence set, can be designed low, by increasing sequencelength N. Therefore, by assigning zero correlation zone sequence sets(multiple sets per cell for system B-3) which differ one another torespective cells, it is possible to sufficiently decrease interferingpower included in the de-spread output.

B-6. Pilot Transmission System.

Let's consider of constructing a pilot transmission system, using theprinciple of basic system B-1 by a similar method to that explained withsystem A-5. This system produces a time sequence s_(k) ^(p)(n_(p))(n_(p)=1,2, . . . N_(p)) consisting of N_(p) pieces of the pilot symbolswhich is made by replacing transmit-data-block d_(k) in FIG. 12( a) bypilot sequence v_(C)(n_(P)), and then inserts them into the same frameas that in FIG. 11 in time division manner. By carrying out the usersignal separation by the method in Eqs. (43) and (45), de-spread pilotresponse p_(k)(n_(p)) can be produced, because s_(k)(n_(p)) is composedof a convolution product of ZCZ sequence Z_(k) and sequencev_(C)(n_(P)).

A response h_(kj)(n_(p)) corresponding to channel characteristic h_(kj)⁰ in Eq. (21) is produced here by obtaining correlation-output betweenp_(k)(n_(p)) and j-shift sequence a(n_(p))(i−j) using analyzing sequencea(n_(p)) in Eq. (20) which is orthogonal to v_(C)(n_(p)) except for the0-shift position. A channel characteristic without a deviation in thefrequency characteristics is obtained, if N_(p) pieces of the responsesproduced in this way are averaged.

From the view point of spectral efficiency and accuracy, this system ismore advantageous than exiting systems, because channel responses whichare perfectly separated from the data and the other user's signals areobtained, in addition to that, the identical pilot symbol slots can beshared by K(=N/2) users.

C. Space Based Orthogonal Transform System.

The multi-output user group transmission systems described with systemsA-3 and A-4 have used technology for increasing the user population byusing multiple receive-antennas. Let's explain here, a SN ratio improvedmulti-output system which can improve the signal-to-noise ratio of thereceived de-spread output by using multiple antennas, as the 11thembodiment example, while referring to the system parameters of systemA-3 and FIG. 8.

Let user population Q belonging to user group U_(k) using orthogonalcarrier wave f_(k) be one, for simplicity, and let the k-th user groupbe u_(k). In this assumption, consider a system in which respective of Kusers transmit transmit-symbols produced by the block spreadingmodulation using K pieces of the carrier waves, and a receiver receivesmultiplexed received symbol r in the e(=1,2, . . . , E)-threceive-antenna of the receiver. E pieces of de-spread data-blocks givenby the following equation, similar to those shown in Eqs. (13) and (14)where the user signals have been separated, are obtained, whendemodulating the symbols with orthogonal carrier wave f_(k) by the meansexplained in system A-1.

γ_(k) ^(e) =H _(k) ^(e) d _(k) +x   (66)

The following de-spread matrix is produced by concatenating outputssimilarly obtained with respect to all the receive-antennas.

X _(k)=(γ_(k) ¹,γ_(k) ², . . . , γ_(k) ^(E))   (67)

This matrix is converted using an orthogonal transform matrix Ω_(k) intoan orthogonalized transformed matrix Y_(k). This process becomes aspatial conversion, when regarding spatially arranged antennas as aspace axis. Let's select Ω_(k) here so that auto-correlation matrix ofmatrix Y_(k)=X_(k)Ω_(k) may become an identity matrix I_(E), and thefollowing equations is satisfied,

E(Y _(k) ^(H) Y _(k))=I _(E)   (68)

where E means taking an ensemble average. This condition can be achievedby obtaining an unitary matrix U_(k) which satisfies the followingequations, using auto-correlation matrix R_(Xk) of X_(k).

$\begin{matrix}\left. \begin{matrix}{{U_{k}^{H}\left( {R_{Xk}^{{- 1}/2}{\hat{H}}_{k}^{H}{\hat{H}}_{k}R_{Xk}^{{- 1}/2}} \right)}U_{k}} \\{= {{diag}\left\lbrack {\lambda_{1},\lambda_{2},\ldots \mspace{14mu},\lambda_{E}} \right\rbrack}} \\{R_{Xk} = {E\left( {X_{k}^{H}X_{k}} \right)}} \\{{\hat{H}}_{k} = \left( {H_{k}^{1},H_{k}^{2},\ldots \mspace{14mu},H_{k}^{E}} \right)}\end{matrix} \right\} & (69)\end{matrix}$

Here, a channel matrix Ĥ_(k) corresponding to user u_(k) is used. Hence,the orthogonal transform matrix is given by the following equation.

Ω_(k) =R _(Xk) ^(−1/2) U _(k)   (70)

The same detected signals can be obtained even if using either X_(k) orY_(k) if there is no noise. The above equations show that Y_(k) consistsof E pieces of the eigen-vectors. Signal to noise ratio SN of the e-thcomponent vector y_(k) ^(e) of Y_(k) is given by the following equation,

$\begin{matrix}{({SN})_{e} = {\frac{E\left\lbrack {y_{k}^{e}}^{2} \right\rbrack}{E\left\lbrack {y_{x}^{e}}^{2} \right\rbrack} = \frac{\lambda_{e}}{1 - \lambda_{e}}}} & (71)\end{matrix}$

where y_(k) ^(e) and y_(x) ^(e) are a signal component and AWGNcomponent included in the above-described component vector, and λ_(e) isan eigen value shown in Eq. (69).

Let's consider a weighting factor so as to give a large weight to thecomponent vector which shows a high SN ratio. As the k-th componentvector y_(k) ^(e) is a demodulated data-block, a soft-output vectord_(k) can be obtained by solving Eq. (14) using channel matrix H_(k). Asynthesized soft-output is produced, by summing products which are madeby multiplying E pieces of vectors d_(k) by the respective weightsstated above. This output has a high SN ratio due to the above-mentionedweighting. Therefore, low error rate transmission can be achieved byusing a detected output vector which are obtained by making it on thehard decisions the soft-output.

An orthogonal transformation on a time basis can be also used as well asthe above-mentioned spatial conversion method. Let a de-spread matrixcomposed of de-spread data-blocks which have been produced from L piecesof symbols by the following equation.

Γ_(k)=(γ_(k) ⁰,γ_(k) ¹, . . . , γ_(k) ^(L−1))   (72)

Here let l(=1,2, . . . l*−1) be the symbol number. This demodulatedmatrix is subjected to an orthogonal transform by the followingequation,

W_(k)=Λ_(k) ^(H)Γ_(k)   (73)

where Λ_(k) is a temporal orthogonal transform matrix.

An unitary matrix such as to satisfy the following equation is chosen,so that auto-correlation matrix U_(k) of matrix W_(k) may bediagonalized by the method stated above.

$\begin{matrix}\left. \begin{matrix}{{U_{k}^{H}\left( {R_{Xk}^{{- 1}/2}{\hat{H}}_{k}^{H}{\hat{H}}_{k}R_{Xk}^{{- 1}/2}} \right)}U_{k}} \\{= {{diag}\left\lbrack {\lambda_{0},\lambda_{1},\ldots \mspace{14mu},\lambda_{L - 1}} \right\rbrack}}\end{matrix} \right\} & (74)\end{matrix}$

Based on this equation, a transform matrix is obtained as follows.

$\begin{matrix}\left. \begin{matrix}{\Lambda_{k} = {R_{\Gamma \; k}^{{- 1}/2}U}} \\{R_{\Gamma \; k} = {E\left( {\Gamma_{k}^{h}\Gamma_{k}} \right)}}\end{matrix} \right\} & (75)\end{matrix}$

The SN ratio of the l-th component vector of transformed matrix W_(k)which have been thus produced, is given by the following equation.

$\begin{matrix}{({SN})_{l} = \frac{\lambda_{l}}{1 - \lambda_{l}}} & (76)\end{matrix}$

Now, let's select weighting based on this ratio. A synthesizedsoft-output can be obtained, by summing products which are made bymultiplying soft-outputs obtained from the respective component vectorsby the weights stated above. Low error rate transmission can be achievedby using outputs which are made by making it on the hard decisions thesynthesized soft-output.

The invention described in claim 1 has solved a problem such that thepeak transmit-power required for obtaining necessary error ratecharacteristics considerably increases (by M² times larger power of thatof single sequence transmission) in case of the conventional repeatedsequence orthogonal carrier wave modulation system, because system (P-7)uses a multiplexed spreading sequence (a sequence made by concurrentlysumming M pieces of spreading sequences each of which is multiplied by atransmit-data for M bit transmission) as each of the data-blocks.

That is to say, the transmit-power of this invention can be considerablyreduced in comparison with that of system (P-7), because this inventionuses data-block of a single sequence consisting of the binary M chipsconveying M bit data without using sequence addition. In addition, thespectral efficiency of system (P-3) decreases, because it is generallynecessary for the receiver to choose a length of said spreading sequence(data-block) such as to satisfy M<L, in order to separate M multiplexedsequences on condition of a good error rate characteristic.

Since this invention uses respective data-blocks, each having a length Mthat is the number of bits of the transmit-data as it is, the system ofthis invention achieves a high spectral efficiency such that spectralefficiency η may take nearly one. Besides, there is an effect such thata system using a low transmit-power can be achieved.

And, system (P-5) which transmits a transmit-symbol made by spreadingguard added data-blocks with an orthogonal sequence set, suffers anexcessive guard sequence overhead, and system (P-6) which transmits atransmit-symbol made by spreading a data-block with a shift orthogonalsequence suffers that the user population decreases to a half ofspreading factor. Therefore, the spectral efficiency of theseconventional systems can not increase. In contrast, this invention hasan effect to achieve reduction in guard sequence and increase in theuser population.

On the other hand, systems (P-2) and (P-3) using a single data spreadingmethod and pilot-data multiplexing symbol transmission system (P-4)suffer an increase in the guard sequence overhead, in case of high datatransmission rate. This invention has a remarkable effect in reducingthe overhead to a small value, because one guard sequence is inserted ineach data-block sequence.

The invention described in claims 2 and 3 has solved such a problem thatthe available user population K is limited to (N−1)/2, despite shiftorthogonal sequence spreading system (P-6) using a shift orthogonalsequence with spreading factor N, requires N times larger bandwidth thanthat of the data-rate. That is to say, this invention can construct asystem so that the user population K increases to (N/2) by thetechnology described in claim 2, and, in addition, to N by using thetechnology described in claim 3.

That is to say, this invention has an effect such as to double the userpopulation, and thereby improve the spectral efficiency η to almost oneby utilizing spreading method with ZCZ sequences, and a newde-correlating technique in the receiver.

The invention described in claims 4 and 5 has solved a problem such thatvarious systems using the conventional block spreading techniques failedto provide effective means to adapt to users' multi-rate demand (ofservices in which multiple access of data transmission ratesintermingle).

Since this invention uses a method such as to allocate both a data-blockrepetition rate and carrier frequency slots or a set of hierarchicalspreading sequences for a multiple stage modulation technique of the ZCZsequences corresponding to a desired data rate, to each user'stransmitter, the inter-rate interference can be avoided. As aconsequence, it has an effect to provide the multi-rate services,without decreasing the comprehensive spectral efficiency of the system.

The invention described in claims 6 and 7, has solved the problem suchthat the spectral efficiency of conventional MMSE multi-user MIMOreception system (P-3) considerably decreases, because system (P-3) hasapplied a multi-input multi-output system (MIMO) to single symboltransmission systems carrying 1 bit, resulting in necessity of a longguard sequence compared to the core sequence for a high data ratetransmission.

As a result of producing a block spread symbol and then transmitting it,this invention established a technique of analyzing a concatenatedvector which is made by concatenating receive-antenna outputs suppliedfrom multiple (E pieces of) antennas installed in the receiver, it hasachieved improvement in the spectral efficiency and reduction in thenoise (decrease in the error rate or decrease in the transmit-power).

That is to say, it is effective that a system using this invention canconsiderably decrease power bandwidth product required for one bittransmission by the system, by increasing spectral efficiency η toalmost a value of E, while achieving low transmit-power consumption.

The invention described in claims 8, 9 and 10 has solved a problem suchthat in the conventional single data spreading systems (P-1) to (P-4),not only inter-cell interference could not be sufficiently removed, butalso intra-cell interference increases, because the systems use a methodof transmitting signals made by multiplying a transmit-symbol by a cellspecific scrambling sequence to avoid inter-cell interference, anddescrambling a received symbol by the scrambling sequence to randomizethe interference coming from the other cells, leading to that theorthogonality between received symbol components considerably reduces.This invention has also solved an additional problem such thatinter-user interference in a cell increases due to multi-path, whenapplying the scrambling sequence multiplication technology toconventional data-block spreading technology used in systems (P-7) to(P-9).

This invention has an effect such that the error rate characteristicsremarkably improves, by considerably reducing the inter-cellinterference, while maintaining user's complete separation function in acell by the following transmit-symbol producing methods. In a system ofthis invention, each transmitter produces a transmit-symbol using a cellspecific core-symbol period allocated to the cell to which thetransmitter belongs, or a cell specific chip rate.

The invention described in claims 11 and 12 has solved a problem suchthat the accuracy of channel characteristics obtained by a conventionalmethod considerably deteriorates, because a conventional system obtainschannel characteristics by transmitting a transmit-symbol composed ofdata and pilot information correspondent real axis and imaginary axiscomponents, as a result interference between the real and imaginarycomponents of the received symbol generates under a condition of themulti-path transmission. And this invention solved a problem such thatan effective pilot transmission method has not been developed for theconventional block spreading transmission systems.

This invention described in claims 1 to 10 provides a simple technologyof acquiring channel characteristics by a method, characterized by thata transmitter produces a transmit-pilot symbol byreplacing atransmit-data-block with a spreading sequence and transmits this symbolon a common pilot time slot shared by the other users, and a receiverobtains the channel characteristics by demodulating a multiplexedreceived pilot symbol corresponding to these pilot symbol to separaterespective user components, and by analyzing each of the separatedoutputs. Since, in this method, the multiple users transmit the pilotsequences, while sharing an identical band and time with a large numberof users. This method has an effect of producing a highly precise pilotresponse with flat frequency characteristic without reducing thespectral efficiency of the system.

The invention described in claims 13 and 14 solved a problem such thatoptimum reception technology of MIMO systems or adaptive array-antennasystems, both using multiple receive antennas for purpose of detecting adesired user component on condition of high SN ratio with multiplepieces of multiplexed received symbols, has not been established. Thisinvention provides technology which utilizes surplus signal dimensionsbased on the multiple antenna outputs (or symbols on multiple timepositions) to improve the SN ratio, resulting in reduction of the errorrate, in contrast to the effect of increasing of the user population Etimes larger which is provided by the invention described in claims 6and 7 using plurality E of antennas.

This invention has an effect of considerably increasing the SN ratio ofsoft outputs corresponding to the transmit-data, by applying orthogonaltransformation to a demodulated matrix consisting of plurality E ofdemodulated outputs to produce a transformed matrix, and by summingweighted components, each is made by multiplying a high SN ratiocomponent of said transformed matrix by a large weighting.

Furthermore, it is also possible to construct a system whichaccommodates E₁ times larger user population and achieves a low errorrate performance by allocating E₁ pieces of receive-antennas operatingaccording to the invention described in claims 6 and 7, and allocatingE₂(=E/E₁) pieces of receive antennas operating to this invention. Thus,two principles can be used together.

1. A data-block spread spectrum communications system, wherein saidcommunications system composed of cells or sectors in each of whichsignal transmission and reception are performed between a base stationand K user stations, comprises a transmitter in each of the userstations having means for producing a block spread transmit-symbol byapplying user specific spectral spreading processing and carrier wavemodulation to a transmit data-block which composed of a time sequence ofplural transmit-data, and transmitting said transmit-symbol, and areceiver having means for receiving a multiplexed received symbolcomposed of user specific received components corresponding to K piecesof said transmit-symbols which all the users have transmitted by saidmeans, and performing all the user signal separation and separation ofrespective data contained in said transmitted data-blocks, using aknowledge of channel characteristics between said transmitters and saidreceiver beforehand acquired, said user specific spectral spreadingprocessing and carrier wave modulation, characterized by that thek(=1,2, . . . , K)-th user transmitter comprises, means for producing acore-symbol with core-symbol period T_(S) made by repeating saiddata-block multiple times, producing a guard added symbol by appending aguard sequence to said core-symbol, and producing a block spread symbolby modulating the k-th orthogonal carrier wave f_(k) belonging to a setof orthogonal carrier waves which differ mutually by an integer times ofthe reciprocal of said core-symbol period by said guard added symbol, asa transmit-symbol, and the receiver comprises, means for producing ademodulated output by demodulating said multiplexed received symbol bythe k-th orthogonal carrier wave f_(k), applying averaging operation inan unit of the data-block to a demodulated core-symbol on the coresymbol period which is made by removing a guard part of said demodulatedoutput, to produce a de-spread data-block corresponding to thedata-block which the k-th user has transmitted, by removing the otheruser signal correspondent received symbol components, and detectingrespective of said transmit-data by making on the hard decisions softoutputs obtained by separating respective transmit-data componentscontained in said de-spread data-block, using said channelcharacteristics.
 2. A data-block spread spectrum communications system,wherein said communications system provides an intra-cell orintra-sector communications services between base station and K users,characterized by that said system comprises means for allocating asequence Z_(k) ⁰ included in zero correlation zone sequence set Z=(Z₁⁰,Z₂ ⁰, . . . Z_(k) ⁰, . . . Z_(N/2) ⁰) with length N to a transmitterof the k(=1,2, . . . , K)-th user u_(k) ⁰ as a spreading sequence, whileallocating a sequence Z_(k) ¹ which is made by shifting sequence Z_(k) ⁰by 1 chip cyclically to the left to a transmitter of the k′(=K+1, K+2, .. . 2K)-th user u_(k) ¹, as a spreading sequence, each of saidtransmitters comprises means for producing a transmit-symbol byspreading a transmit-data-block composed of a time sequence of pluraltransmit-data by a method of making Kronecker product of said spreadingsequence and said transmit-data-block, and transmitting saidtransmit-symbol using a user common carrier wave, and a receivercomprises, means for producing a multiplexed demodulated symbol bydemodulating a multiplexed received symbol corresponding totransmit-symbols which all the users similarly have transmitted by saidcarrier wave, and carrying out separation of respective usercorrespondent received symbol components and separation of respectivetransmitted data contained in each of said transmit-data-blocks usingsaid multiplexed demodulated symbol and said spreading sequences, meansfor producing respective de-spread data-blocks γ_(k) ^(Q)(Q=0,1) byde-spreading said multiplexed demodulated symbol by respective of saidsequences Z_(k) ^(Q) to make a de-spread output, and applying averagingprocessing to the de-spread output, producing approximated soft outputs{tilde over (d)}_(k) ^(Q) of transmit-data blocks d_(k) ^(Q) byde-correlating said respective de-spread data-blocks using a principalwave channel matrix H_(k0) ^(Q) and a delayed wave channel matrix H_(k1)^(Q), and a receiver comprises means for producing a system ofde-correlating equations using an approximated concatenated soft outputvector made by concatenating said approximated soft outputs, an unknownvector made by concatenating said transmit-data-blocks d_(k) ^(Q) and ade-correlating matrix made by a correlation function between saidchannel matrices H_(k0) ^(Q) and H_(k1) ^(Q), and means for detectingdata which said two users have transmitted, by making hard decisionseach component of a soft output vector obtained by solving said systemof de-correlating equations, and thereby composing a system with which Nusers can simultaneously transmit transmit-symbols using said zerocorrelation zone sequence set with a family size N/2.
 3. (canceled) 4.The data-block spread spectrum communications system, according to claim1 to perform multiple data-rate transmission, characterized by that saidtransmitter of the k-th user comprises, means for producing a guardadded symbol by appending a guard sequence to a core-symbol which ismade by repeating N times a data-block of a length M, and a transmitterof the k′-th user comprises, means for producing another guard addedsymbol of which transmission data-rate ratio compared to the formertakes n:1 for an integer n by appending a guard sequence to acore-symbol which is made by repeating Nn times a data-block of a lengthM/n such as to be an integer, and has the same core-symbol period asthat of the former core-symbol, and respective user transmitterscomprise, means for producing transmit-symbols by modulating the k-thand the k′-th orthogonal carrier waves, respectively and choosing 0 orseveral kinds of transmit-symbols corresponding to values of ngenerally, and transmitting said transmit-symbols using said orthogonalcarrier waves such that the spectrum of these transmit-symbols do notoverlap one another, and said receiver comprises, means for producingseparately demodulated data-blocks corresponding to the respectiveuser's transmit-symbols by demodulating a received core-symbol which ismade by removing the guard part from said multiplexed received symbol byrespective of the k-th and the k′-th orthogonal carrier waves.
 5. Thedata-block spread spectrum communications system, according to claim 2to perform multiple data-rate transmission, characterized by that saidtransceiver system comprises, means for preparing a zero correlationzone sequence set Z^(n)=(Z₁ ^(n),Z₂ ^(n), . . . ) as spreading sequencesof the n(=1,2, . . . )-th layer, in advance, and producing a synthesizedsequence Y₂ ¹ by obtaining a Kronecker product of the first sequencebelonging to the second layer and the second sequence belonging to thefirst layer, and a base station comprises, means for allocatingsequences belonging to one or multiple spreading layers corresponding totransmit-data rate, and each user's transmitter comprises means forproducing base-band spreading symbols by obtaining Kronecker products ofa synthesized sequence Y which has been produced on the basis ofspreading sequences (Z¹,Z², . . . ) allocated to respective of saidlayers and transmit-data-block, and transmitting a carrier wavemodulated guard added symbol which is made by appending a guard sequenceto each of said multistage block spread symbols, and said receivercomprises, means for producing the said demodulated core symbol bydemodulating said multiplexed received symbol by the carrier wave, andseparately producing each of demodulated data-blocks such as not tocontain demodulated components corresponding to the othertransmit-symbols by de-spreading said core-symbol with said synthesizedsequences.
 6. The data-block spread spectrum communications system,according to claim 1 or 4, characterized by that each of the usertransmitters of the k(=1,2, . . . K)-th user group in a system, of whichusers are divided by K user groups, each user group having plurality Qof users, comprises, means for modulating the k-th orthogonal carrierwave f_(k) by said guard added data-block repeated sequence, and saidreceiver equipped with multiple receive-antennas with antenna ordinalnumber e(=1,2, . . . E) comprises, means for producing a demodulatedsymbol by modulating a multiplexed received symbol which has receivedvia the e-th antenna with the k-th orthogonal carrier wave f_(k) and,separately producing a multiplexed de-spread data-block corresponding todata-blocks which the k-th user group has transmitted, by applying theaveraging operation to a demodulated core symbol made by removing theguard part from said demodulated symbol, to remove signal components ofthe other user groups, means for producing a concatenated de-spreadvector by concatenating E pieces of said multiplexed de-spreaddata-blocks, producing a soft output vector by solving a system oflinear equations with multiple unknowns, composed of an extended channelmatrix which is made of Q times E pieces of the channel characteristicsbetween respective users of the k-th user group and thereceive-antennas, said concatenated de-spread vector, and an unknownvector corresponding to the transmit-data of the Q users, and obtainingdetected data of the respective users belonging to said respectivegroups by making it on the hard decisions respective components of saidsoft output vector.
 7. The data-block spread spectrum communicationssystem, according to claim 2 or 5, characterized by that saidtransmitter of the k(=1,2, . . . K)-th user group in a system, of whichusers are divided by K user groups, each user group having plurality Qof users, comprises, means for producing a data-block spread symbolusing the k-th spreading sequence Z_(k) belonging to said zerocorrelation zone sequence set, and said receiver equipped with multiplereceive-antennas with antenna ordinal number e(=1,2, . . . E) comprises,means for producing a demodulated symbol by demodulating a multiplexedreceived symbol which has received via the e-th antenna with a carrierwave, separately producing a multiplexed de-spread data-blockcorresponding to data-blocks which the k-th user group has transmitted,by applying de-spreading operation to a demodulated core symbol made byremoving the guard part from said demodulated symbol with said spreadingsequence Z_(k) to produce de-spread output, and applying the averagingoperation to said de-spread output to remove signal components of theother user groups, and means for producing a concatenated demodulatedvector by concatenating E pieces of said multiplexed de-spreaddata-block, producing a soft output vector by solving a system of linearequations with multiple unknowns, composed of an extended channel matrixwhich is made of Q times E pieces of the channel characteristics betweenrespective users of the k-th user group and the receive-antennas, saidconcatenated demodulated vector, and an unknown vector corresponding tothe transmit-data of the Q users, and obtaining transmit-data of therespective users belonging to said respective groups by making it on thehard decisions respective components of said soft output vector.
 8. Thedata-block spread spectrum communications system, according to any oneof claims 1, 2, 4 and 5, characterized by that said transmitterbelonging to each cell comprises, means for producing said data-blockrepeated sequence or said data-block spread symbol over a cell specifictransmit-core-block spreading period which is allocated to said cellbeforehand, producing a transmit-symbol by modulating the carrier wavedescribed in any one of claims 1, 2, 4 and 5 by a base-band guard addedsymbol made by appending a guard sequence to said core symbol, andtransmitting said transmit-symbol, and said receiver comprises, meansfor producing a demodulated core-symbol on a received timingsynchronized with said cell specific transmit-core block spreadingperiod using said multiplexed received symbol and said carrier wavewhich the transmitter has used, and thereby producing a demodulateddata-block with suppressed inter-cell interfering components, byapplying the same processing to said demodulated core-symbol as themethod described in any one of claims 1, 2, 4 and
 5. 9. The data-blockspread spectrum communications system, according to any one of claims 1,2, 4 and 5, characterized by that said transmitter belonging to eachcell comprises, means for producing a guard added data-block repeatedsequence or a guard added data-block spread symbol using a cell specificchip rate made by summing a chip rate bias which is allocated to saidcell beforehand to a nominal chip rate, producing a transmit-symbol bymodulating one of the said carrier waves described in any one of claims1, 2, 4 and 5, and transmitting said transmit-symbol, and said receivercomprises, means for producing a correlation output between amultiplexed demodulated symbol with continuous waveform which has beenproduced using said carrier wave and a chip waveform on said cellspecific chip rate, producing a discrete time sequence having theamplitude of said correlation output as a demodulated core-symbol, andapplying said averaging processing to an output made by de-spreadingsaid demodulated core-symbol by the method described in any one ofclaims 1, 2, 4 and 5, to produce a de-spread data-block where aninter-cell interfering component is suppressed.
 10. (canceled)
 11. Thedata-block spread spectrum communications system, according to claim 1or 2, characterized by that each of said transmitters comprises, meansfor producing a transmit-symbol by substituting a pilot sequence foreach of said transmit-data-blocks according to claim 1 or 2 as a pilotsymbol, and transmitting said pilot symbol over a cell common pilot timeslot, under a condition of quasi-synchronous or synchronoustransmission, and said receiver comprises, means for producing ademodulated pilot response by demodulating, de-spreading and applyingaveraging processing to a multiplexed received pilot symbol extracted bythe method described in claim 1 or 2, and obtaining a channelcharacteristic based on a correlation output between the j(=0,1,2, . . ., J−1) shift analyzing sequence a_(j) of an analyzing sequenceorthogonal to said pilot sequence except at 0 shift position and saiddemodulated pilot response.
 12. The data-block spread spectrumcommunications system, according to claim 11, characterized by that saidtransmitter comprises, means for preparing a pilot sequence setconsisting of multiple (N_(p)) pieces of pilot sequences of whichfrequency spectra complement each other, producing N_(p) pieces of pilotsymbols by such a method that each of them is constructed using a pilotsequence selected out of said pilot sequence set as a transmit-pilotsymbol, and transmitting these N_(p) pieces of transmit-pilot symbolsperiodically, and said receiver comprises, means for preparing ananalyzing sequence orthogonal to each of said pilot sequences except atthe 0 shift position, obtaining N_(p) pieces of channel characteristicsusing respective of received pilot symbols and said correspondinganalyzing sequences, and producing a precise pilot response by taking amean value of these N_(p) pieces of channel characteristics as a pilotcharacteristic.
 13. The data-block spread spectrum communicationssystem, according to claim 6, characterized by that said receivercomprises, means for producing a de-spread matrix X_(k) using E piecesof said de-spread data-block γ_(k) ^(e)(e=1,2, . . . , E) addressed tothe k-th user which has been produced with the e-th receive-antennaoutput, and producing a transformed matrix Y_(k) by multiplying saidde-spread matrix by such an orthogonal transform matrix Ω_(k) thatautocorrelation matrix of said transformed matrix may be diagonalized,means for selecting a weighting corresponding to the eigen value of saidtransformed matrix for the e-th transformed component y_(k) ^(e),obtaining a soft output vector {tilde over (d)}_(k) ^(e) correspondingto said component y_(k) ^(e) by a method of solving a system of multiplelinear equations, and means for producing a detected data vector{circumflex over (d)}_(k) corresponding to said transmit-symbol bymaking it on the hard decisions an output vector which is made bysumming some of said soft output vectors, each is multiplied by saidweighting.
 14. The data-block spread spectrum communications system,according to claim 13, characterized by that said receiver comprises,means for producing a transformed matrix W_(k) by applying orthogonaltransform to a de-spread matrix Γ_(k) consisting of L pieces ofde-spread data-block γ_(k) ^(l) which has been produced with a symbol onthe l(=1,2, . . . , L)-th time position by the method described in claim6 with such an orthogonal transform matrix Λ_(k) that an autocorrelationmatrix of transformed matrix W_(k) may be diagonalized, and selectingfor a soft output vector w_(k) ^(l) of said transformed matrix W_(k),and a weighting corresponding to the l-th eigen-value of transformedmatrix W_(k), and means for producing a detected data of the k-th userusing an output vector made by summing some of soft output vectors w_(k)^(l) each is multiplied by said weighting.
 15. The data-block spreadspectrum communications system, according to claim 6, characterized bythat said transmitter belonging to each cell comprises, means forproducing said data-block repeated sequence or said data-block spreadsymbol over a cell specific transmit-core-block spreading period whichis allocated to said cell beforehand, producing a transmit-symbol bymodulating the carrier wave described in any one of claims 1, 2, 4 and 5by a base-band guard added symbol made by appending a guard sequence tosaid core symbol, and transmitting said transmit-symbol, and saidreceiver comprises, means for producing a demodulated core-symbol on areceived timing synchronized with said cell specific transmit-core blockspreading period using said multiplexed received symbol and said carrierwave which the transmitter has used, and thereby producing a demodulateddata-block with suppressed inter-cell interfering components, byapplying the same processing to said demodulated core-symbol as themethod described in any one of claims 1, 2, 4 and
 5. 16. The data-blockspread spectrum communications system, according to claim 7,characterized by that said transmitter belonging to each cell comprises,means for producing said data-block repeated sequence or said data-blockspread symbol over a cell specific transmit-core-block spreading periodwhich is allocated to said cell beforehand, producing a transmit-symbolby modulating the carrier wave described in any one of claims 1, 2, 4and 5 by a base-band guard added symbol made by appending a guardsequence to said core symbol, and transmitting said transmit-symbol, andsaid receiver comprises, means for producing a demodulated core-symbolon a received timing synchronized with said cell specific transmit-coreblock spreading period using said multiplexed received symbol and saidcarrier wave which the transmitter has used, and thereby producing ademodulated data-block with suppressed inter-cell interferingcomponents, by applying the same processing to said demodulatedcore-symbol as the method described in any one of claims 1, 2, 4 and 5.17. The data-block spread spectrum communications system, according toclaim 6, characterized by that said transmitter belonging to each cellcomprises, means for producing a guard added data-block repeatedsequence or a guard added data-block spread symbol using a cell specificchip rate made by summing a chip rate bias which is allocated to saidcell beforehand to a nominal chip rate, producing a transmit-symbol bymodulating one of the said carrier waves described in any one of claims1, 2, 4 and 5, and transmitting said transmit-symbol, and said receivercomprises, means for producing a correlation output between amultiplexed demodulated symbol with continuous waveform which has beenproduced using said carrier wave and a chip waveform on said cellspecific chip rate, producing a discrete time sequence having theamplitude of said correlation output as a demodulated core-symbol, andapplying said averaging processing to an output made by de-spreadingsaid demodulated core-symbol by the method described in any one ofclaims 1, 2, 4 and 5, to produce a de-spread data-block where aninter-cell interfering component is suppressed.
 18. The data-blockspread spectrum communications system, according to claim 7,characterized by that said transmitter belonging to each cell comprises,means for producing a guard added data-block repeated sequence or aguard added data-block spread symbol using a cell specific chip ratemade by summing a chip rate bias which is allocated to said cellbeforehand to a nominal chip rate, producing a transmit-symbol bymodulating one of the said carrier waves described in any one of claims1, 2, 4 and 5, and transmitting said transmit-symbol, and said receivercomprises, means for producing a correlation output between amultiplexed demodulated symbol with continuous waveform which has beenproduced using said carrier wave and a chip waveform on said cellspecific chip rate, producing a discrete time sequence having theamplitude of said correlation output as a demodulated core-symbol, andapplying said averaging processing to an output made by de-spreadingsaid demodulated core-symbol by the method described in any one ofclaims 1, 2, 4 and 5, to produce a de-spread data-block where aninter-cell interfering component is suppressed.
 19. The data-blockspread spectrum communications system, according to claim 7,characterized by that said receiver comprises, means for producing ade-spread matrix X_(k) using E pieces of said de-spread data-block γ_(k)^(e)(e=1,2, . . . , E) addressed to the k-th user which has beenproduced with the e-th receive-antenna output, and producing atransformed matrix Y_(k) by multiplying said de-spread matrix by such anorthogonal transform matrix Ω_(k) that autocorrelation matrix of saidtransformed matrix may be diagonalized, means for selecting a weightingcorresponding to the eigen value of said transformed matrix for the e-thtransformed component y_(k) ^(e), obtaining a soft output vector {tildeover (d)}_(k) ^(e) corresponding to said component y_(k) ^(e) by amethod of solving a system of multiple linear equations, and means forproducing a detected data vector {circumflex over (d)}_(k) correspondingto said transmit-symbol by making it on the hard decisions an outputvector which is made by summing some of said soft output vectors, eachis multiplied by said weighting.
 20. The data-block spread spectrumcommunications system, according to claim 19, characterized by that saidreceiver comprises, means for producing a transformed matrix W_(k) byapplying orthogonal transform to a de-spread matrix Γ_(k) consisting ofL pieces of de-spread data-block γ_(k) ^(l) which has been produced witha symbol on the l(=1,2, . . . , L)-th time position by the methoddescribed in claim 7 with such an orthogonal transform matrix Λ_(k) thatan autocorrelation matrix of transformed matrix W_(k) may bediagonalized, and selecting for a soft output vector w_(k) ^(l) of saidtransformed matrix W_(k), and a weighting corresponding to the l-theigen-value of transformed matrix W_(k), and means for producing adetected data of the k-th user using an output vector made by summingsome of soft output vectors w_(k) ^(l) each is multiplied by saidweighting.